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authorRichard Guy Briggs <rgb@redhat.com>2021-08-23 22:04:09 -0400
committerPaul Moore <paul@paul-moore.com>2021-08-24 18:52:36 -0400
commit67d69e9d1a6c889d98951c1d74b19332ce0565af (patch)
tree9dc62b09fe7c96ec05736b532959b26959d07b75 /kernel
parentd97e99386ad0dcae08cb0f0c70efa806a2d4811c (diff)
audit: move put_tree() to avoid trim_trees refcount underflow and UAF
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/audit_tree.c2
1 files changed, 1 insertions, 1 deletions
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 */

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