2020-04-30 11:22:59

by YoungJun.park

Subject: [PATCH] fs: kernfs: fix possible null pointer dereferences

kernfs_path_from_node_locked checks buf is NULL.
But, two cases below are not covered.

if(!kn_to) <--- case1 (buf can be NULL)
return strlcpy(buf, "(null)", buflen);

if(kn_from == kn_to) <--- case2 (buf can be NULL)
return strlcpy(buf, "/", buflen);

if (!buf) <--- checked here.
return -EINVAL;

buf NULL case needs to be checked first.

Signed-off-by: youngjun <[email protected]>
---
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 02fb5cc76e33..d802cfceddba 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -128,6 +128,9 @@ 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);

@@ -137,9 +140,6 @@ 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;
--
2.17.1

2020-05-06 12:46:28

by Greg Kroah-Hartman

Subject: Re: [PATCH] fs: kernfs: fix possible null pointer dereferences

On Thu, Apr 30, 2020 at 04:20:46AM -0700, youngjun wrote:
> kernfs_path_from_node_locked checks buf is NULL.
> But, two cases below are not covered.
>
> if(!kn_to) <--- case1 (buf can be NULL)
> return strlcpy(buf, "(null)", buflen);
>
> if(kn_from == kn_to) <--- case2 (buf can be NULL)
> return strlcpy(buf, "/", buflen);
>
> if (!buf) <--- checked here.
> return -EINVAL;
>
> buf NULL case needs to be checked first.
>
> Signed-off-by: youngjun <[email protected]>
> ---
> fs/kernfs/dir.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)

I have 3 patches here from you, with the same subject lines, yet they do
different things.

I'm dropping them all, can you please resend a patch series of the
remaining patches you wish us to review for kernfs?

thanks,

greg k-h