AUDIT_TRIM is expected to be idempotent, but multiple executions resulted in a
refcount underflow and use-after-free.
git bisect fingered commit fb041bb7c0a918b95c6889fc965cdc4a75b4c0ca (2019-11)
("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 8432c70062978d9a57bde6715496d585ec520c3e (2018-11)
("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.
Fixes: 8432c7006297 ("audit: Simplify locking around untag_chunk()")
Signed-off-by: Richard Guy Briggs <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Seiji Nishikawa <[email protected]>
---
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 b2be4e978ba3..2cd7b5694422 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -593,7 +593,6 @@ static void prune_tree_chunks(struct audit_tree *victim,
bool tagged)
spin_lock(&hash_lock);
}
spin_unlock(&hash_lock);
- put_tree(victim);
}
/*
@@ -602,6 +601,7 @@ 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 */
--
2.27.0
--
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