From 0634c0f91995da57435377cdb40f39d13aed0f16 Mon Sep 17 00:00:00 2001 From: Richard Guy Briggs Date: Mon, 23 Aug 2021 22:04:09 -0400 Subject: [PATCH] audit: move put_tree() to avoid trim_trees refcount underflow and UAF 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 Cc: Will Deacon Cc: Alexander Viro Cc: Seiji Nishikawa Cc: stable@vger.kernel.org Fixes: 8432c7006297 ("audit: Simplify locking around untag_chunk()") Signed-off-by: Richard Guy Briggs Reviewed-by: Jan Kara [PM: reformatted/cleaned-up the commit description] Signed-off-by: Paul Moore Signed-off-by: Greg Kroah-Hartman --- kernel/audit_tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c index e49c912f862d..9dec6314cd28 100644 --- a/kernel/audit_tree.c +++ b/kernel/audit_tree.c @@ -595,7 +595,6 @@ static void prune_tree_chunks(struct audit_tree *victim, bool tagged) spin_lock(&hash_lock); } spin_unlock(&hash_lock); - put_tree(victim); } /* @@ -604,6 +603,7 @@ static void prune_tree_chunks(struct audit_tree *victim, bool tagged) static void prune_one(struct audit_tree *victim) { prune_tree_chunks(victim, false); + put_tree(victim); } /* trim the uncommitted chunks from tree */