block: Check ADMIN before NICE for IOPRIO_CLASS_RT
Subsystems (4)
PATCH v2 1/1 block: Check ADMIN before NICE for IOPRIO_CLASS_RT
Booting to Android userspace on 5.14 or newer triggers the following SELinux denial:
avc: denied { sys_nice } for comm="init" capability=23
scontext=u:r:init:s0 tcontext=u:r:init:s0 tclass=capability permissive=0
Init is PID 0 running as root, so it already has CAP_SYS_ADMIN. For better compatibility with older SEPolicy, check ADMIN before NICE.
---
v2: added comment requested by Jens
block/ioprio.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
block/ioprio.c +8 -1
@@ -69,7 +69,14 @@ int ioprio_check_cap(int ioprio)switch (class) {case IOPRIO_CLASS_RT : -if (!capable (CAP_SYS_NICE ) && !capable (CAP_SYS_ADMIN )) +/* +* Originally this only checked for CAP_SYS_ADMIN, +* which was implicitly allowed for pid 0 by security +* modules such as SELinux. Make sure we check +* CAP_SYS_ADMIN first to avoid a denial/avc for +* possibly missing CAP_SYS_NICE permission. +*/ +if (!capable (CAP_SYS_ADMIN ) && !capable (CAP_SYS_NICE ))return -EPERM ; fallthrough;/* rt has prio field too */
Signature · 1 line
2.34.0.rc1.387.gb447b232ab-goog
Quoted 38 lines · Alistair Delva
Booting to Android userspace on 5.14 or newer triggers the following SELinux denial:
avc: denied {
sys_nice} for comm="init" capability=23
scontext=u:r:init:s0 tcontext=u:r:init:s0 tclass=capability permissive=0Init is PID 0 running as root, so it already has
CAP_SYS_ADMIN. For better compatibility with older SEPolicy, check ADMIN before NICE.Fixes 9d3a39a5f1e4 ("block: grant IOPRIO_CLASS_RT to CAP_SYS_NICE")Signed-off-by Alistair Delva <[email protected]>Cc Khazhismel Kumykov <[email protected]>Cc Bart Van Assche <[email protected]>Cc Serge Hallyn <[email protected]>Cc Jens Axboe <[email protected]>Cc Greg Kroah-Hartman <[email protected]>Cc Paul Moore <[email protected]>Cc [email protected] # v5.14+---
v2: added comment requested by Jensblock/ioprio.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)block/ioprio.c +1
-1@@ -69,7 +69,14 @@ int ioprio_check_cap(int ioprio)switch (class) {case IOPRIO_CLASS_RT : -if (!capable (CAP_SYS_NICE ) && !capable (CAP_SYS_ADMIN )) +/*
block/ioprio.c int ioprio_check_cap(int ioprio) · line 82
Quoted 10 lines
block/ioprio.c +7
-0+* Originally this only checked for CAP_SYS_ADMIN, +* which was implicitly allowed for pid 0 by security +* modules such as SELinux. Make sure we check +* CAP_SYS_ADMIN first to avoid a denial/avc for +* possibly missing CAP_SYS_NICE permission. +*/ +if (!capable (CAP_SYS_ADMIN ) && !capable (CAP_SYS_NICE ))return -EPERM ; fallthrough;/* rt has prio field too */
Are there any other SELinux policies (Fedora?) that need to be verified?
Anyway:
Quoted 7 lines · Alistair Delva
Booting to Android userspace on 5.14 or newer triggers the following SELinux denial:
avc: denied {
sys_nice} for comm="init" capability=23
scontext=u:r:init:s0 tcontext=u:r:init:s0 tclass=capability permissive=0
Quoted 8 lines
Init is PID 0 running as root, so it already has
CAP_SYS_ADMIN. For better compatibility with older SEPolicy, check ADMIN before NICE.Fixes 9d3a39a5f1e4 ("block: grant IOPRIO_CLASS_RT to CAP_SYS_NICE")Signed-off-by Alistair Delva <[email protected]>Cc Khazhismel Kumykov <[email protected]>Cc Bart Van Assche <[email protected]>Cc Serge Hallyn <[email protected]>
This won't harm anything, so
but questions below.
Quoted 17 lines
Cc Jens Axboe <[email protected]>Cc Greg Kroah-Hartman <[email protected]>Cc Paul Moore <[email protected]>Cc [email protected] # v5.14+---
v2: added comment requested by Jensblock/ioprio.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)block/ioprio.c +0
-0
block/ioprio.c int ioprio_check_cap(int ioprio) · line 74
Quoted 7 lines
block/ioprio.c +3
-1@@ -69,7 +69,14 @@ int ioprio_check_cap(int ioprio)switch (class) {case IOPRIO_CLASS_RT : -if (!capable (CAP_SYS_NICE ) && !capable (CAP_SYS_ADMIN )) +/* +* Originally this only checked for CAP_SYS_ADMIN, +* which was implicitly allowed for pid 0 by security
What do you mean, implicitly allowed for pid 0? Can you point to where that happens?
block/ioprio.c int ioprio_check_cap(int ioprio) · line 80
Quoted 6 lines
block/ioprio.c +5
-0+* modules such as SELinux. Make sure we check +* CAP_SYS_ADMIN first to avoid a denial/avc for +* possibly missing CAP_SYS_NICE permission. +*/ +if (!capable (CAP_SYS_ADMIN ) && !capable (CAP_SYS_NICE ))return -EPERM ;
But whichever one comes first can cause an avc denial message. It seems like we need a new capable() primitive which supports multiple bits, when more than one can authorize an action, and which emits an audit message only if all bits are missing.
Quoted 4 lines
block/ioprio.c +0
-0fallthrough;/* rt has prio field too */ Signature · 1 line
2.34.0.rc1.387.gb447b232ab-goog
Quoted 8 lines · Alistair Delva
Booting to Android userspace on 5.14 or newer triggers the following SELinux denial:
avc: denied {
sys_nice} for comm="init" capability=23
scontext=u:r:init:s0 tcontext=u:r:init:s0 tclass=capability permissive=0[...]
Applied, thanks!
[1/1] block: Check ADMIN before NICE for IOPRIO_CLASS_RT
commit: 94c4b4fd25e6c3763941bdec3ad54f2204afa992
Best regards,
Signature · 1 line
Jens Axboe