diff options
| author | Tejun Heo <tj@kernel.org> | 2022-01-06 11:02:28 -1000 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2022-01-06 11:02:28 -1000 |
| commit | 1756d7994ad85c2479af6ae5a9750b92324685af (patch) | |
| tree | a18dad688da376a60325e2d1ee34187f16a50bde /kernel/cgroup/cgroup-v1.c | |
| parent | 75acfdb6fd922598a408a0d864486aeb167c1a97 (diff) | |
| download | linux-1756d7994ad85c2479af6ae5a9750b92324685af.tar.bz2 | |
cgroup: Use open-time credentials for process migraton perm checks
cgroup process migration permission checks are performed at write time as
whether a given operation is allowed or not is dependent on the content of
the write - the PID. This currently uses current's credentials which is a
potential security weakness as it may allow scenarios where a less
privileged process tricks a more privileged one into writing into a fd that
it created.
This patch makes both cgroup2 and cgroup1 process migration interfaces to
use the credentials saved at the time of open (file->f_cred) instead of
current's.
Reported-by: "Eric W. Biederman" <ebiederm@xmission.com>
Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Fixes: 187fe84067bd ("cgroup: require write perm on common ancestor when moving processes on the default hierarchy")
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup/cgroup-v1.c')
| -rw-r--r-- | kernel/cgroup/cgroup-v1.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 81c9e0685948..0e7369103ba6 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -504,10 +504,11 @@ static ssize_t __cgroup1_procs_write(struct kernfs_open_file *of, goto out_unlock; /* - * Even if we're attaching all tasks in the thread group, we only - * need to check permissions on one of them. + * Even if we're attaching all tasks in the thread group, we only need + * to check permissions on one of them. Check permissions using the + * credentials from file open to protect against inherited fd attacks. */ - cred = current_cred(); + cred = of->file->f_cred; tcred = get_task_cred(task); if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) && !uid_eq(cred->euid, tcred->uid) && |