* [PATCH] fs: kernfs: Fix possible null-pointer dereferences in kernfs_path_from_node_locked()
@ 2019-07-24 2:22 Jia-Ju Bai
2019-07-29 18:51 ` Tejun Heo
0 siblings, 1 reply; 2+ messages in thread
From: Jia-Ju Bai @ 2019-07-24 2:22 UTC (permalink / raw)
To: gregkh, tj; +Cc: linux-kernel, Jia-Ju Bai
In kernfs_path_from_node_locked(), there is an if statement on line 147
to check whether buf is NULL:
if (buf)
When buf is NULL, it is used on line 151:
len += strlcpy(buf + len, parent_str, ...)
and line 158:
len += strlcpy(buf + len, "/", ...)
and line 160:
len += strlcpy(buf + len, kn->name, ...)
Thus, possible null-pointer dereferences may occur.
To fix these possible bugs, buf is checked before being used.
If it is NULL, -EINVAL is returned.
These bugs are found by a static analysis tool STCheck written by us.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
fs/kernfs/dir.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index a387534c9577..9b01f6ce1d79 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -137,6 +137,9 @@ 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;
@@ -144,8 +147,7 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
depth_to = kernfs_depth(common, kn_to);
depth_from = kernfs_depth(common, kn_from);
- if (buf)
- buf[0] = '\0';
+ buf[0] = '\0';
for (i = 0; i < depth_from; i++)
len += strlcpy(buf + len, parent_str,
--
2.17.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] fs: kernfs: Fix possible null-pointer dereferences in kernfs_path_from_node_locked()
2019-07-24 2:22 [PATCH] fs: kernfs: Fix possible null-pointer dereferences in kernfs_path_from_node_locked() Jia-Ju Bai
@ 2019-07-29 18:51 ` Tejun Heo
0 siblings, 0 replies; 2+ messages in thread
From: Tejun Heo @ 2019-07-29 18:51 UTC (permalink / raw)
To: Jia-Ju Bai; +Cc: gregkh, linux-kernel
On Wed, Jul 24, 2019 at 10:22:42AM +0800, Jia-Ju Bai wrote:
> In kernfs_path_from_node_locked(), there is an if statement on line 147
> to check whether buf is NULL:
> if (buf)
>
> When buf is NULL, it is used on line 151:
> len += strlcpy(buf + len, parent_str, ...)
> and line 158:
> len += strlcpy(buf + len, "/", ...)
> and line 160:
> len += strlcpy(buf + len, kn->name, ...)
>
> Thus, possible null-pointer dereferences may occur.
>
> To fix these possible bugs, buf is checked before being used.
> If it is NULL, -EINVAL is returned.
>
> These bugs are found by a static analysis tool STCheck written by us.
Can we just get rid of the NULL testing?
Thanks.
--
tejun
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2019-07-24 2:22 [PATCH] fs: kernfs: Fix possible null-pointer dereferences in kernfs_path_from_node_locked() Jia-Ju Bai
2019-07-29 18:51 ` Tejun Heo
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