[PATCH] cifs_dbg() outputs an uninitialized buffer in cifs_readdir()

[PATCH] cifs_dbg() outputs an uninitialized buffer in cifs_readdir()

[Vasily Averin]

In some cases tmp_bug can be not filled in cifs_filldir and stay uninitialized,
therefore its printk with "%s" modifier can leak content of kernelspace memory.
If old content of this buffer does not contain '\0' access bejond end of
allocated object can crash the host.

Signed-off-by: Vasily Averin <vvs-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
---
 fs/cifs/readdir.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 0557c45..b30a4a6 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -847,6 +847,7 @@ int cifs_readdir(struct file *file, struct dir_context *ctx)
 		 * if buggy server returns . and .. late do we want to
 		 * check for that here?
 		 */
+		*tmp_buf = 0;
 		rc = cifs_filldir(current_entry, file, ctx,
 				  tmp_buf, max_len);
 		if (rc) {
-- 
1.9.1

Re: [PATCH] cifs_dbg() outputs an uninitialized buffer in cifs_readdir()

[Steve French]

merged into cifs-2.6.git and added cc:stable

Let me know if other cifs/smb3 patches planned for 4.5

On Thu, Jan 14, 2016 at 4:41 AM, Vasily Averin <vvs-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org> wrote:
> In some cases tmp_bug can be not filled in cifs_filldir and stay uninitialized,
> therefore its printk with "%s" modifier can leak content of kernelspace memory.
> If old content of this buffer does not contain '\0' access bejond end of
> allocated object can crash the host.
>
> Signed-off-by: Vasily Averin <vvs-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
> ---
>  fs/cifs/readdir.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
> index 0557c45..b30a4a6 100644
> --- a/fs/cifs/readdir.c
> +++ b/fs/cifs/readdir.c
> @@ -847,6 +847,7 @@ int cifs_readdir(struct file *file, struct dir_context *ctx)
>                  * if buggy server returns . and .. late do we want to
>                  * check for that here?
>                  */
> +               *tmp_buf = 0;
>                 rc = cifs_filldir(current_entry, file, ctx,
>                                   tmp_buf, max_len);
>                 if (rc) {
> --
> 1.9.1
>
> --
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-- 
Thanks,

Steve