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| author | Ronny Chevalier <ronny.chevalier@hp.com> | 2018-07-11 14:39:37 +0200 |
|---|---|---|
| committer | Paul Moore <paul@paul-moore.com> | 2018-07-18 11:43:36 -0400 |
| commit | baa2a4fdd525c8c4b0f704d20457195b29437839 (patch) | |
| tree | 3f84ac6375623358fb1bfe69fd3c97a51de7f169 /kernel/audit_watch.c | |
| parent | 290e44b7dd116cc61cf37b7ca0be13313bb11e37 (diff) | |
| download | linux-baa2a4fdd525c8c4b0f704d20457195b29437839.tar.bz2 | |
audit: fix use-after-free in audit_add_watch
audit_add_watch stores locally krule->watch without taking a reference
on watch. Then, it calls audit_add_to_parent, and uses the watch stored
locally.
Unfortunately, it is possible that audit_add_to_parent updates
krule->watch.
When it happens, it also drops a reference of watch which
could free the watch.
How to reproduce (with KASAN enabled):
auditctl -w /etc/passwd -F success=0 -k test_passwd
auditctl -w /etc/passwd -F success=1 -k test_passwd2
The second call to auditctl triggers the use-after-free, because
audit_to_parent updates krule->watch to use a previous existing watch
and drops the reference to the newly created watch.
To fix the issue, we grab a reference of watch and we release it at the
end of the function.
Signed-off-by: Ronny Chevalier <ronny.chevalier@hp.com>
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Diffstat (limited to 'kernel/audit_watch.c')
| -rw-r--r-- | kernel/audit_watch.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c index 6f249bdf2d84..787c7afdf829 100644 --- a/kernel/audit_watch.c +++ b/kernel/audit_watch.c @@ -420,6 +420,13 @@ int audit_add_watch(struct audit_krule *krule, struct list_head **list) struct path parent_path; int h, ret = 0; + /* + * When we will be calling audit_add_to_parent, krule->watch might have + * been updated and watch might have been freed. + * So we need to keep a reference of watch. + */ + audit_get_watch(watch); + mutex_unlock(&audit_filter_mutex); /* Avoid calling path_lookup under audit_filter_mutex. */ @@ -428,8 +435,10 @@ int audit_add_watch(struct audit_krule *krule, struct list_head **list) /* caller expects mutex locked */ mutex_lock(&audit_filter_mutex); - if (ret) + if (ret) { + audit_put_watch(watch); return ret; + } /* either find an old parent or attach a new one */ parent = audit_find_parent(d_backing_inode(parent_path.dentry)); @@ -447,6 +456,7 @@ int audit_add_watch(struct audit_krule *krule, struct list_head **list) *list = &audit_inode_hash[h]; error: path_put(&parent_path); + audit_put_watch(watch); return ret; } |