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Subject[PATCH] kernfs: fix potential null-ptr-deref in kernfs_path_from_node_locked()
Date
Ensure that the 'buf' is not empty before strlcpy() uses it.

Commit bbe70e4e4211 ("fs: kernfs: Fix possible null-pointer dereferences
in kernfs_path_from_node_locked()") first noticed this, but it didn't
fix it completely.

Fixes: 9f6df573a404 ("kernfs: Add API to generate relative kernfs path")
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
fs/kernfs/dir.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index f33b3baad07cb36..b2422265c86edf2 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -140,6 +140,9 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
size_t depth_from, depth_to, len = 0;
int i, j;

+ if (!buf)
+ return -EINVAL;
+
if (!kn_to)
return strlcpy(buf, "(null)", buflen);

@@ -149,9 +152,6 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
if (kn_from == kn_to)
return strlcpy(buf, "/", buflen);

- if (!buf)
- return -EINVAL;
-
common = kernfs_common_ancestor(kn_from, kn_to);
if (WARN_ON(!common))
return -EINVAL;
--
2.25.1
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