From: Dan Carpenter <dan.carpenter@linaro.org>
Date: Fri, 12 Jan 2024 06:59:41 +0000 (+0300)
Subject: netfs, fscache: Prevent Oops in fscache_put_cache()
X-Git-Tag: v6.8-rc2~28^2^2~6
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3be0b3ed1d76c6703b9ee482b55f7e01c369cc68;p=thirdparty%2Flinux.git

netfs, fscache: Prevent Oops in fscache_put_cache()

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>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/e84bc740-3502-4f16-982a-a40d5676615c@moroto.mountain/ # v2
---

diff --git a/fs/netfs/fscache_cache.c b/fs/netfs/fscache_cache.c
index d645f8b302a27..9397ed39b0b4e 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);