4.9-stable review patch. If anyone has any objections, please let me know.
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From: Ronny Chevalier ronny.chevalier@hp.com
[ Upstream commit baa2a4fdd525c8c4b0f704d20457195b29437839 ]
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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/audit_watch.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
--- a/kernel/audit_watch.c +++ b/kernel/audit_watch.c @@ -419,6 +419,13 @@ int audit_add_watch(struct audit_krule * 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. */ @@ -427,8 +434,10 @@ int audit_add_watch(struct audit_krule * /* 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)); @@ -446,6 +455,7 @@ int audit_add_watch(struct audit_krule * *list = &audit_inode_hash[h]; error: path_put(&parent_path); + audit_put_watch(watch); return ret; }