linux-kernel - [PATCH] cifs: check pointer before freeing

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Date:   Tue,  5 Jan 2021 12:21:26 -0800
From:   trix@...hat.com
To:     sfrench@...ba.org, natechancellor@...il.com,
        ndesaulniers@...gle.com, aaptel@...e.com, palcantara@...e.de
Cc:     linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Tom Rix <trix@...hat.com>
Subject: [PATCH] cifs: check pointer before freeing

From: Tom Rix <trix@...hat.com>

clang static analysis reports this problem

dfs_cache.c:591:2: warning: Argument to kfree() is a constant address
  (18446744073709551614), which is not memory allocated by malloc()
        kfree(vi);
        ^~~~~~~~~

In dfs_cache_del_vol() the volume info pointer 'vi' being freed
is the return of a call to find_vol().  The large constant address
is find_vol() returning an error.

Add an error check to dfs_cache_del_vol() similar to the one done
in dfs_cache_update_vol().

Fixes: 54be1f6c1c37 ("cifs: Add DFS cache routines")
Signed-off-by: Tom Rix <trix@...hat.com>
---
 fs/cifs/dfs_cache.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index 6ad6ba5f6ebe..0fdb0de7ff86 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -1260,7 +1260,8 @@ void dfs_cache_del_vol(const char *fullpath)
 	vi = find_vol(fullpath);
 	spin_unlock(&vol_list_lock);
 
-	kref_put(&vi->refcnt, vol_release);
+	if (!IS_ERR(vi))
+		kref_put(&vi->refcnt, vol_release);
 }
 
 /**
-- 
2.27.0