fanotify: Allow user space to pass back additional audit info

The Fanotify API can be used for access control by requesting permission event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the decision. If this information were available in the audit trail, policy writers can close the loop on debugging policy. Also, if this additional information were available, it would enable the creation of tools that can suggest changes to the policy similar to how audit2allow can help refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended information is organized with headers containing a type and size that can be delegated to interested subsystems. One new information type is defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel will behave as expected and reject a newer userspace, leaving it up to the newer userspace to test appropriately and adapt as necessary. This is done by providing a a fully-formed FAN_INFO extension but setting the fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit record, whereas on an older kernel it will fail.

The audit function was updated to log the additional information in the AUDIT_FANOTIFY record. The following are examples of the new record format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1
fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2

changelog:
v1:
- first version by Steve Grubb <[email protected]>

Link https://lore.kernel.org/r/2042449.irdbgypaU6@x2 open here

v2:
- enhancements suggested by Jan Kara <[email protected]>
- 1/3 change %d to %u in pr_debug
- 2/3 change response from __u32 to __u16
- mod struct fanotify_response and fanotify_perm_event add extra_info_type, extra_info_buf - extra_info_buf size max FANOTIFY_MAX_RESPONSE_EXTRA_LEN, add struct fanotify_response_audit_rule - extend debug statements
- remove unneeded macros
- [internal] change interface to finish_permission_event() and process_access_response() - 3/3 update format of extra information
- [internal] change interface to audit_fanotify()
- change ctx_type= to fan_type=

Link https://lore.kernel.org/r/[email protected] open here

v3:
- 1/3 switch {,__}audit_fanotify() from uint to u32
- 2/3 re-add fanotify_get_response switch case FAN_DENY: to avoid unnecessary churn - add FAN_EXTRA flag to indicate more info and break with old kernel - change response from u16 to u32 to avoid endian issues
- change extra_info_buf to union
- move low-cost fd check earlier
- change FAN_RESPONSE_INFO_AUDIT_NONE to FAN_RESPONSE_INFO_NONE
- switch to u32 for internal and __u32 for uapi

Link https://lore.kernel.org/all/[email protected] open here

v4:
- scrap FAN_INVALID_RESPONSE_MASK in favour of original to catch invalid response == 0 - introduce FANOTIFY_RESPONSE_* macros
- uapi: remove union
- keep original struct fanotify_response, add fan_info infra starting with audit reason - uapi add struct fanotify_response_info_header{type/pad/len} and struct fanotify_response_info_audit_rule{hdr/rule} - rename fan_ctx= to fan_info=, FAN_EXTRA to FAN_INFO
- change event struct from type/buf to len/buf
- enable multiple info extensions in one message
- hex encode fan_info in __audit_fanotify()
- record type FANOTIFY extended to "type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=3F" Link:
https://lore.kernel.org/all/[email protected]

v5:
- fixed warnings in p2/4 and p3/4 found by <[email protected]>
- restore original behaviour for !FAN_INFO case and fanotify_get_response()
- rename member audit_rule to rule_number
- eliminate memory leak of info_buf on failure (no longer dynamic)
- rename buf:info, count:info_len, c:remain, ib:infop
- fix pr_debug
- return -ENOENT on FAN_INFO and fd==FAN_NOFD to signal new kernel
- fanotify_write() remove redundant size check
- add u32 subj_trust obj_trust fields with unknown value "2"
- split out to helper process_access_response_info()
- restore finish_permission_event() response_struct to u32
- assume and enforce one rule to audit, pass struct directly to __audit_fanotify() - change fanotify_perm_event struct to union hdr/audir_rule
- add vspace to fanotify_write() and process_access_response_info()
- squash 3/4 with 4/4
- fix v3 and v4 links

Link https://lore.kernel.org/all/[email protected] open here

v6:
- simplify __audit_fanotify() from audit_log_format/audit_log_n_hex to audit_log/%X - add comment to clarify {subj,obj}_trust values
- remove fd processing from process_access_response_info()
- return info_len immediately from process_access_response() on FAN_NOFD after process_access_response_info() Link:
https://lore.kernel.org/all/[email protected]

v7:
- change non FAN_INFO case to "0"
- change from if-return to switch(type)-case, which now ignores non-audit info Link: https://lore.kernel.org/all/[email protected]

Richard Guy Briggs (3):
fanotify: Ensure consistent variable type for response
fanotify: define struct members to hold response decision context fanotify,audit: Allow audit to use the full permission event response

 fs/notify/fanotify/fanotify.c      |  8 ++-
 fs/notify/fanotify/fanotify.h      |  6 +-
 fs/notify/fanotify/fanotify_user.c | 88 ++++++++++++++++++++++--------
 include/linux/audit.h              |  9 +--
 include/linux/fanotify.h           |  5 ++
 include/uapi/linux/fanotify.h      | 30 +++++++++-
 kernel/auditsc.c                   | 18 +++++-
 7 files changed, 131 insertions(+), 33 deletions(-)

The Fanotify API can be used for access control by requesting permission event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the decision. If this information were available in the audit trail, policy writers can close the loop on debugging policy. Also, if this additional information were available, it would enable the creation of tools that can suggest changes to the policy similar to how audit2allow can help refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended information is organized with headers containing a type and size that can be delegated to interested subsystems. One new information type is defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel will behave as expected and reject a newer userspace, leaving it up to the newer userspace to test appropriately and adapt as necessary. This is done by providing a a fully-formed FAN_INFO extension but setting the fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit record, whereas on an older kernel it will fail.

The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record
format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2

changelog:
v1:
- first version by Steve Grubb <[email protected]>

Link https://lore.kernel.org/r/2042449.irdbgypaU6@x2 open here

v2:
- enhancements suggested by Jan Kara <[email protected]>
- 1/3 change %d to %u in pr_debug
- 2/3 change response from __u32 to __u16
- mod struct fanotify_response and fanotify_perm_event add extra_info_type, extra_info_buf
- extra_info_buf size max FANOTIFY_MAX_RESPONSE_EXTRA_LEN, add struct fanotify_response_audit_rule
- extend debug statements
- remove unneeded macros
- [internal] change interface to finish_permission_event() and process_access_response()
- 3/3 update format of extra information
- [internal] change interface to audit_fanotify()
- change ctx_type= to fan_type=

Link https://lore.kernel.org/r/[email protected] open here

v3:
- 1/3 switch {,__}audit_fanotify() from uint to u32
- 2/3 re-add fanotify_get_response switch case FAN_DENY: to avoid unnecessary churn
- add FAN_EXTRA flag to indicate more info and break with old kernel
- change response from u16 to u32 to avoid endian issues
- change extra_info_buf to union
- move low-cost fd check earlier
- change FAN_RESPONSE_INFO_AUDIT_NONE to FAN_RESPONSE_INFO_NONE
- switch to u32 for internal and __u32 for uapi

Link https://lore.kernel.org/all/[email protected] open here

v4:
- scrap FAN_INVALID_RESPONSE_MASK in favour of original to catch invalid response == 0
- introduce FANOTIFY_RESPONSE_* macros
- uapi: remove union
- keep original struct fanotify_response, add fan_info infra starting with audit reason
- uapi add struct fanotify_response_info_header{type/pad/len} and struct fanotify_response_info_audit_rule{hdr/rule}
- rename fan_ctx= to fan_info=, FAN_EXTRA to FAN_INFO
- change event struct from type/buf to len/buf
- enable multiple info extensions in one message
- hex encode fan_info in __audit_fanotify()
- record type FANOTIFY extended to "type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=3F"

Link https://lore.kernel.org/all/[email protected] open here

v5:
- fixed warnings in p2/4 and p3/4 found by <[email protected]>
- restore original behaviour for !FAN_INFO case and fanotify_get_response()
- rename member audit_rule to rule_number
- eliminate memory leak of info_buf on failure (no longer dynamic)
- rename buf:info, count:info_len, c:remain, ib:infop
- fix pr_debug
- return -ENOENT on FAN_INFO and fd==FAN_NOFD to signal new kernel
- fanotify_write() remove redundant size check
- add u32 subj_trust obj_trust fields with unknown value "2"
- split out to helper process_access_response_info()
- restore finish_permission_event() response_struct to u32
- assume and enforce one rule to audit, pass struct directly to __audit_fanotify()
- change fanotify_perm_event struct to union hdr/audir_rule
- add vspace to fanotify_write() and process_access_response_info()
- squash 3/4 with 4/4
- fix v3 and v4 links

Link https://lore.kernel.org/all/[email protected] open here

v6:
- simplify __audit_fanotify() from audit_log_format/audit_log_n_hex to audit_log/%X
- add comment to clarify {subj,obj}_trust values
- remove fd processing from process_access_response_info()
- return info_len immediately from process_access_response() on FAN_NOFD after process_access_response_info()

Link https://lore.kernel.org/all/[email protected] open here

v7:
- change non FAN_INFO case to "0"
- change from if-return to switch(type)-case, which now ignores non-audit info

Link https://lore.kernel.org/all/[email protected] open here

Richard Guy Briggs (3):
fanotify: Ensure consistent variable type for response
fanotify: define struct members to hold response decision context fanotify,audit: Allow audit to use the full permission event response

 fs/notify/fanotify/fanotify.c      |  8 ++-
 fs/notify/fanotify/fanotify.h      |  6 +-
 fs/notify/fanotify/fanotify_user.c | 88 ++++++++++++++++++++++--------
 include/linux/audit.h              |  9 +--
 include/linux/fanotify.h           |  5 ++
 include/uapi/linux/fanotify.h      | 30 +++++++++-
 kernel/auditsc.c                   | 18 +++++-
 7 files changed, 131 insertions(+), 33 deletions(-)

Signature · 1 line

2.27.0

Quoted 23 lines · Richard Guy Briggs

The Fanotify API can be used for access control by requesting permission event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the decision. If this information were available in the audit trail, policy writers can close the loop on debugging policy. Also, if this additional information were available, it would enable the creation of tools that can suggest changes to the policy similar to how audit2allow can help refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended information is organized with headers containing a type and size that can be delegated to interested subsystems. One new information type is defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel will behave as expected and reject a newer userspace, leaving it up to the newer userspace to test appropriately and adapt as necessary. This is done by providing a a fully-formed FAN_INFO extension but setting the fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit record, whereas on an older kernel it will fail.

Quoted 5 lines

The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record
format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2

Thanks! I've applied this series to my tree.

Quoted 30 lines · Jan Kara

Quoted 28 lines · Richard Guy Briggs

The Fanotify API can be used for access control by requesting permission event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the decision. If this information were available in the audit trail, policy writers can close the loop on debugging policy. Also, if this additional information were available, it would enable the creation of tools that can suggest changes to the policy similar to how audit2allow can help refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended information is organized with headers containing a type and size that can be delegated to interested subsystems. One new information type is defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel will behave as expected and reject a newer userspace, leaving it up to the newer userspace to test appropriately and adapt as necessary. This is done by providing a a fully-formed FAN_INFO extension but setting the fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit record, whereas on an older kernel it will fail.

The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record
format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2

Quoted 1 line

Thanks! I've applied this series to my tree.

While I think this version of the patchset is fine, for future reference it would have been nice if you had waited for my ACK on patch 3/3; while Steve maintains his userspace tools, I'm the one responsible for maintaining the Linux Kernel's audit subsystem.

Quoted 31 lines · Paul Moore

Quoted 30 lines · Jan Kara

Quoted 28 lines · Richard Guy Briggs

The Fanotify API can be used for access control by requesting permission event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the decision. If this information were available in the audit trail, policy writers can close the loop on debugging policy. Also, if this additional information were available, it would enable the creation of tools that can suggest changes to the policy similar to how audit2allow can help refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended information is organized with headers containing a type and size that can be delegated to interested subsystems. One new information type is defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel will behave as expected and reject a newer userspace, leaving it up to the newer userspace to test appropriately and adapt as necessary. This is done by providing a a fully-formed FAN_INFO extension but setting the fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit record, whereas on an older kernel it will fail.

The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record
format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2

Quoted 6 lines

Quoted 1 line

Thanks! I've applied this series to my tree.

While I think this version of the patchset is fine, for future reference it would have been nice if you had waited for my ACK on patch 3/3; while Steve maintains his userspace tools, I'm the one responsible for maintaining the Linux Kernel's audit subsystem.

Aha, I'm sorry for that. I had the impression that on the last version of the series you've said you don't see anything for which the series should be respun so once Steve's objections where addressed and you were silent for a few days, I thought you consider the thing settled... My bad.

Quoted 56 lines · Jan Kara

Quoted 48 lines · Paul Moore

Quoted 47 lines · Jan Kara

Quoted 46 lines · Richard Guy Briggs

The Fanotify API can be used for access control by requesting permission
event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the
decision. If this information were available in the audit trail, policy
writers can close the loop on debugging policy. Also, if this additional
information were available, it would enable the creation of tools that
can suggest changes to the policy similar to how audit2allow can help
refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended
information is organized with headers containing a type and size that
can be delegated to interested subsystems. One new information type is
defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel
will behave as expected and reject a newer userspace, leaving it up to
the newer userspace to test appropriately and adapt as necessary. This
is done by providing a a fully-formed FAN_INFO extension but setting the
fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit
record, whereas on an older kernel it will fail.

The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record

format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2> > >

Quoted 6 lines

Quoted 1 line

Thanks! I've applied this series to my tree.

While I think this version of the patchset is fine, for future reference it would have been nice if you had waited for my ACK on patch 3/3; while Steve maintains his userspace tools, I'm the one responsible for maintaining the Linux Kernel's audit subsystem.

Quoted 4 lines

Aha, I'm sorry for that. I had the impression that on the last version of the series you've said you don't see anything for which the series should be respun so once Steve's objections where addressed and you were silent for a few days, I thought you consider the thing settled... My bad.

That's understandable, especially given inconsistencies across subsystems. If it helps, if I'm going to ACK something I make it explicit with a proper 'Acked-by: ...' line in my reply; if I say something looks good but there is no explicit ACK, there is usually something outstanding that needs to be resolved, e.g. questions, additional testing, etc.

In this particular case I posed some questions in that thread and never saw a reply with any answers, hence the lack of an ACK. While I think the patches were reasonable, I withheld my ACK until the questions were answered ... which they never were from what I can tell, we just saw a new patchset with changes.

/me shrugs

Quoted 69 lines · EST Paul Moore

Quoted 56 lines · Jan Kara

Quoted 48 lines · Paul Moore

Quoted 47 lines · Jan Kara

Quoted 46 lines · Richard Guy Briggs

The Fanotify API can be used for access control by requesting permission
event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the
decision. If this information were available in the audit trail, policy
writers can close the loop on debugging policy. Also, if this additional
information were available, it would enable the creation of tools that
can suggest changes to the policy similar to how audit2allow can help
refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended
information is organized with headers containing a type and size that
can be delegated to interested subsystems. One new information type is
defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel
will behave as expected and reject a newer userspace, leaving it up to
the newer userspace to test appropriately and adapt as necessary. This
is done by providing a a fully-formed FAN_INFO extension but setting the
fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit
record, whereas on an older kernel it will fail.

The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record

format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2> > >

Quoted 6 lines

Quoted 1 line

Thanks! I've applied this series to my tree.

While I think this version of the patchset is fine, for future reference it would have been nice if you had waited for my ACK on patch 3/3; while Steve maintains his userspace tools, I'm the one responsible for maintaining the Linux Kernel's audit subsystem.

Quoted 4 lines

Aha, I'm sorry for that. I had the impression that on the last version of the series you've said you don't see anything for which the series should be respun so once Steve's objections where addressed and you were silent for a few days, I thought you consider the thing settled... My bad.

That's understandable, especially given inconsistencies across subsystems. If it helps, if I'm going to ACK something I make it explicit with a proper 'Acked-by: ...' line in my reply; if I say something looks good but there is no explicit ACK, there is usually something outstanding that needs to be resolved, e.g. questions, additional testing, etc.

Quoted 7 lines

In this particular case I posed some questions in that thread and never saw a reply with any answers, hence the lack of an ACK. While I think the patches were reasonable, I withheld my ACK until the questions were answered ... which they never were from what I can tell, we just saw a new patchset with changes.

/me shrugs

Paul,

I reread the thread. You only had a request to change if/else to a switch construct only if there was a respin for the 3F. You otherwise said get Steve's input and the 3F borders on being overly clever. Both were addressed. If you had other questions that needed answers on, please restate them to expedite approval of this set of patches. As far as I can tell, all comments are addressed.

Quoted 78 lines · Steve Grubb

Quoted 69 lines · EST Paul Moore

Quoted 56 lines · Jan Kara

Quoted 48 lines · Paul Moore

Quoted 47 lines · Jan Kara

Quoted 46 lines · Richard Guy Briggs

The Fanotify API can be used for access control by requesting permission
event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the
decision. If this information were available in the audit trail, policy
writers can close the loop on debugging policy. Also, if this additional
information were available, it would enable the creation of tools that
can suggest changes to the policy similar to how audit2allow can help
refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended
information is organized with headers containing a type and size that
can be delegated to interested subsystems. One new information type is
defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel
will behave as expected and reject a newer userspace, leaving it up to
the newer userspace to test appropriately and adapt as necessary. This
is done by providing a a fully-formed FAN_INFO extension but setting the
fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit
record, whereas on an older kernel it will fail.

The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record

format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2> > >

Quoted 6 lines

Quoted 1 line

Thanks! I've applied this series to my tree.

While I think this version of the patchset is fine, for future reference it would have been nice if you had waited for my ACK on patch 3/3; while Steve maintains his userspace tools, I'm the one responsible for maintaining the Linux Kernel's audit subsystem.

Quoted 4 lines

Aha, I'm sorry for that. I had the impression that on the last version of the series you've said you don't see anything for which the series should be respun so once Steve's objections where addressed and you were silent for a few days, I thought you consider the thing settled... My bad.

That's understandable, especially given inconsistencies across subsystems. If it helps, if I'm going to ACK something I make it explicit with a proper 'Acked-by: ...' line in my reply; if I say something looks good but there is no explicit ACK, there is usually something outstanding that needs to be resolved, e.g. questions, additional testing, etc.

Quoted 7 lines

In this particular case I posed some questions in that thread and never saw a reply with any answers, hence the lack of an ACK. While I think the patches were reasonable, I withheld my ACK until the questions were answered ... which they never were from what I can tell, we just saw a new patchset with changes.

/me shrugs

Quoted 8 lines

Paul,

I reread the thread. You only had a request to change if/else to a switch construct only if there was a respin for the 3F. You otherwise said get Steve's input and the 3F borders on being overly clever. Both were addressed. If you had other questions that needed answers on, please restate them to expedite approval of this set of patches. As far as I can tell, all comments are addressed.

Steve,

It might be helpful to reread my reply below:

https://lore.kernel.org/linux-audit/CAHC9VhRWDD6Tk6AEmgoobBkcVKRYbVOte7-F0TGJD2dRk7NKxw@mail.gmail.com/

You'll see that I made a comment in that email about not following Richard's explanation about "encoding the zero" (the patch was encoding a "?" to the best I could tell). I was hoping for some clarification from Richard on his comments, and I never saw anything in my inbox. I just checked the archives on lore and I don't see anything there either.

paul-moore.com

Quoted 92 lines · Paul Moore

Quoted 78 lines · Steve Grubb

Quoted 69 lines · EST Paul Moore

Quoted 56 lines · Jan Kara

Quoted 48 lines · Paul Moore

Quoted 47 lines · Jan Kara

Quoted 46 lines · Richard Guy Briggs

The Fanotify API can be used for access control by requesting permission
event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the
decision. If this information were available in the audit trail, policy
writers can close the loop on debugging policy. Also, if this additional
information were available, it would enable the creation of tools that
can suggest changes to the policy similar to how audit2allow can help
refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended
information is organized with headers containing a type and size that
can be delegated to interested subsystems. One new information type is
defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel
will behave as expected and reject a newer userspace, leaving it up to
the newer userspace to test appropriately and adapt as necessary. This
is done by providing a a fully-formed FAN_INFO extension but setting the
fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit
record, whereas on an older kernel it will fail.

The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record

format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2> > >

Quoted 6 lines

Quoted 1 line

Thanks! I've applied this series to my tree.

While I think this version of the patchset is fine, for future reference it would have been nice if you had waited for my ACK on patch 3/3; while Steve maintains his userspace tools, I'm the one responsible for maintaining the Linux Kernel's audit subsystem.

Quoted 4 lines

Aha, I'm sorry for that. I had the impression that on the last version of the series you've said you don't see anything for which the series should be respun so once Steve's objections where addressed and you were silent for a few days, I thought you consider the thing settled... My bad.

That's understandable, especially given inconsistencies across subsystems. If it helps, if I'm going to ACK something I make it explicit with a proper 'Acked-by: ...' line in my reply; if I say something looks good but there is no explicit ACK, there is usually something outstanding that needs to be resolved, e.g. questions, additional testing, etc.

Quoted 7 lines

In this particular case I posed some questions in that thread and never saw a reply with any answers, hence the lack of an ACK. While I think the patches were reasonable, I withheld my ACK until the questions were answered ... which they never were from what I can tell, we just saw a new patchset with changes.

/me shrugs

Quoted 8 lines

Paul,

I reread the thread. You only had a request to change if/else to a switch construct only if there was a respin for the 3F. You otherwise said get Steve's input and the 3F borders on being overly clever. Both were addressed. If you had other questions that needed answers on, please restate them to expedite approval of this set of patches. As far as I can tell, all comments are addressed.

Steve,

It might be helpful to reread my reply below:

Quoted 8 lines

https://lore.kernel.org/linux-audit/CAHC9VhRWDD6Tk6AEmgoobBkcVKRYbVOte7-F0TGJD2dRk7NKxw@mail.gmail.com/

You'll see that I made a comment in that email about not following Richard's explanation about "encoding the zero" (the patch was encoding a "?" to the best I could tell). I was hoping for some clarification from Richard on his comments, and I never saw anything in my inbox. I just checked the archives on lore and I don't see anything there either.

Well, it could have been any of:

        ?
        "?"
        3F
        30
        0

I can't answer that. My preference is for 3F but good arguments can be made for any of these. I defer to Steve since it is his tools and customers that have to deal with it.

Quoted 39 lines · Jan Kara

Quoted 31 lines · Paul Moore

Quoted 30 lines · Jan Kara

Quoted 28 lines · Richard Guy Briggs

The Fanotify API can be used for access control by requesting permission event notification. The user space tooling that uses it may have a complicated policy that inherently contains additional context for the decision. If this information were available in the audit trail, policy writers can close the loop on debugging policy. Also, if this additional information were available, it would enable the creation of tools that can suggest changes to the policy similar to how audit2allow can help refine labeled security.

This patchset defines a new flag (FAN_INFO) and new extensions that define additional information which are appended after the response structure returned from user space on a permission event. The appended information is organized with headers containing a type and size that can be delegated to interested subsystems. One new information type is defined to audit the triggering rule number.

A newer kernel will work with an older userspace and an older kernel will behave as expected and reject a newer userspace, leaving it up to the newer userspace to test appropriately and adapt as necessary. This is done by providing a a fully-formed FAN_INFO extension but setting the fd to FAN_NOFD. On a capable kernel, it will succeed but issue no audit record, whereas on an older kernel it will fail.

The audit function was updated to log the additional information in the
AUDIT_FANOTIFY record. The following are examples of the new record
format:
type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 subj_trust=3 obj_trust=5 type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 subj_trust=2 obj_trust=2

Quoted 6 lines

Quoted 1 line

Thanks! I've applied this series to my tree.

While I think this version of the patchset is fine, for future reference it would have been nice if you had waited for my ACK on patch 3/3; while Steve maintains his userspace tools, I'm the one responsible for maintaining the Linux Kernel's audit subsystem.

Quoted 4 lines

Aha, I'm sorry for that. I had the impression that on the last version of the series you've said you don't see anything for which the series should be respun so once Steve's objections where addressed and you were silent for a few days, I thought you consider the thing settled... My bad.

That's understandable, especially given inconsistencies across subsystems. If it helps, if I'm going to ACK something I make it explicit with a proper 'Acked-by: ...' line in my reply; if I say something looks good but there is no explicit ACK, there is usually something outstanding that needs to be resolved, e.g. questions, additional testing, etc.