From: Dan Carpenter <dan.carpenter@linaro.org>
To: David Howells <dhowells@redhat.com>
Cc: Jeff Layton <jlayton@kernel.org>,
linux-cachefs@redhat.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: [PATCH v2] netfs, fscache: Prevent Oops in fscache_put_cache()
Date: Fri, 12 Jan 2024 09:59:41 +0300 [thread overview]
Message-ID: <e84bc740-3502-4f16-982a-a40d5676615c@moroto.mountain> (raw)
This function dereferences "cache" and then checks if it's
IS_ERR_OR_NULL(). Check first, then dereference.
Fixes: 9549332df4ed ("fscache: Implement cache registration")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
v2: My first version introduced a race and a possible use after free.
fs/netfs/fscache_cache.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/netfs/fscache_cache.c b/fs/netfs/fscache_cache.c
index d645f8b302a2..9397ed39b0b4 100644
--- a/fs/netfs/fscache_cache.c
+++ b/fs/netfs/fscache_cache.c
@@ -179,13 +179,14 @@ EXPORT_SYMBOL(fscache_acquire_cache);
void fscache_put_cache(struct fscache_cache *cache,
enum fscache_cache_trace where)
{
- unsigned int debug_id = cache->debug_id;
+ unsigned int debug_id;
bool zero;
int ref;
if (IS_ERR_OR_NULL(cache))
return;
+ debug_id = cache->debug_id;
zero = __refcount_dec_and_test(&cache->ref, &ref);
trace_fscache_cache(debug_id, ref - 1, where);
--
2.43.0
reply other threads:[~2024-01-12 6:59 UTC|newest]
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