[PATCH 5.10 023/152] cifs: check pointer before freeing

[Greg Kroah-Hartman]

From: Tom Rix <trix@xxxxxxxxxx>

commit 77b6ec01c29aade01701aa30bf1469acc7f2be76 upstream.

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@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
CC: <stable@xxxxxxxxxxxxxxx> # v5.0+
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/cifs/dfs_cache.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -1317,7 +1317,8 @@ void dfs_cache_del_vol(const char *fullp
 	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);
 }
 
 /**