devices cgroup: allow mkfifo
PATCH 1/1 devices cgroup: allow mkfifo
The devcgroup_inode_permission() hook in the devices whitelist cgroup has always bypassed access checks on fifos. But the mknod hook did not. The devices whitelist is only about block and char devices, and fifos can't even be added to the whitelist, so fifos can't be created at all except by tasks which have 'a' in their whitelist (meaning they have access to all devices).
Fix the behavior by bypassing access checks to mkfifo.
--- security/device_cgroup.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)
security/device_cgroup.c +3 -0
@@ -513,6 +513,9 @@ int devcgroup_inode_mknod(int mode, dev_t dev)struct dev_cgroup *dev_cgroup;struct dev_whitelist_item *wh; +if (!S_ISBLK (mode) && !S_ISCHR (mode)) +return 0 ; +rcu_read_lock (); dev_cgroup =task_devcgroup (current);
Signature · 1 line
1.5.4.3
Quoted 9 lines · Serge E. Hallyn
The
devcgroup_inode_permission()hook in the devices whitelist cgroup has always bypassed access checks on fifos. But the mknod hook did not. The devices whitelist is only about block and char devices, and fifos can't even be added to the whitelist, so fifos can't be created at all except by tasks which have 'a' in their whitelist (meaning they have access to all devices).Fix the behavior by bypassing access checks to mkfifo.
It also bypasses checks to mksock. Should backport this patch?
Quoted 19 lines
Signed-off-by Serge E. Hallyn <[email protected]>--- security/device_cgroup.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)security/device_cgroup.c +3
-0@@ -513,6 +513,9 @@ int devcgroup_inode_mknod(int mode, dev_t dev)struct dev_cgroup *dev_cgroup;struct dev_whitelist_item *wh; +if (!S_ISBLK (mode) && !S_ISCHR (mode)) +return 0 ; +rcu_read_lock (); dev_cgroup =task_devcgroup (current);
Quoted 10 lines · Li Zefan
CC AndrewQuoted 7 lines · Serge E. Hallyn
The
devcgroup_inode_permission()hook in the devices whitelist cgroup has always bypassed access checks on fifos. But the mknod hook did not. The devices whitelist is only about block and char devices, and fifos can't even be added to the whitelist, so fifos can't be created at all except by tasks which have 'a' in their whitelist (meaning they have access to all devices).
Quoted 4 lines
Quoted 2 lines
Fix the behavior by bypassing access checks to mkfifo.
It also bypasses checks to mksock. Should backport this patch?
Do you mean push it into -stable?
Couldn't hurt, but it's a DOS to root in a container, not a security vulnerability, and since noone has complainted until now so at least it's not panick-worthy.
Quoted 1 line
Reviewed-by Li Zefan <[email protected]>
Thanks. I'll go ahead and send to Linus and -stable.
-serge
Quoted 19 lines
Quoted 19 lines
Signed-off-by Serge E. Hallyn <[email protected]>--- security/device_cgroup.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)security/device_cgroup.c +3
-0@@ -513,6 +513,9 @@ int devcgroup_inode_mknod(int mode, dev_t dev)struct dev_cgroup *dev_cgroup;struct dev_whitelist_item *wh; +if (!S_ISBLK (mode) && !S_ISCHR (mode)) +return 0 ; +rcu_read_lock (); dev_cgroup =task_devcgroup (current);