Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.14 11/11] audit: move put_tree() to avoid trim_trees refcount underflow and UAF | Date | Wed, 1 Sep 2021 14:29:19 +0200 |
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From: Richard Guy Briggs <rgb@redhat.com>
commit 67d69e9d1a6c889d98951c1d74b19332ce0565af upstream.
AUDIT_TRIM is expected to be idempotent, but multiple executions resulted in a refcount underflow and use-after-free.
git bisect fingered commit fb041bb7c0a9 ("locking/refcount: Consolidate implementations of refcount_t") but this patch with its more thorough checking that wasn't in the x86 assembly code merely exposed a previously existing tree refcount imbalance in the case of tree trimming code that was refactored with prune_one() to remove a tree introduced in commit 8432c7006297 ("audit: Simplify locking around untag_chunk()")
Move the put_tree() to cover only the prune_one() case.
Passes audit-testsuite and 3 passes of "auditctl -t" with at least one directory watch.
Cc: Jan Kara <jack@suse.cz> Cc: Will Deacon <will@kernel.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Seiji Nishikawa <snishika@redhat.com> Cc: stable@vger.kernel.org Fixes: 8432c7006297 ("audit: Simplify locking around untag_chunk()") Signed-off-by: Richard Guy Briggs <rgb@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> [PM: reformatted/cleaned-up the commit description] Signed-off-by: Paul Moore <paul@paul-moore.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- kernel/audit_tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/audit_tree.c +++ b/kernel/audit_tree.c @@ -593,7 +593,6 @@ static void prune_tree_chunks(struct aud spin_lock(&hash_lock); } spin_unlock(&hash_lock); - put_tree(victim); } /* @@ -602,6 +601,7 @@ static void prune_tree_chunks(struct aud static void prune_one(struct audit_tree *victim) { prune_tree_chunks(victim, false); + put_tree(victim); } /* trim the uncommitted chunks from tree */
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