* [PATCHv3] Fix range checks in kernfs_get_target_path
@ 2018-07-07 17:52 Bernd Edlinger
2018-08-26 10:55 ` Bernd Edlinger
0 siblings, 1 reply; 3+ messages in thread
From: Bernd Edlinger @ 2018-07-07 17:52 UTC (permalink / raw)
To: Greg Kroah-Hartman, Tejun Heo, linux-kernel@vger.kernel.org
The terminating NUL byte is only there because the buffer is
allocated with kzalloc(PAGE_SIZE, GFP_KERNEL), but since the
range-check is off-by-one, and PAGE_SIZE==PATH_MAX, the
returned string may not be zero-terminated if it is exactly
PATH_MAX characters long. Furthermore also the initial loop
may theoretically exceed PATH_MAX and cause a fault.
Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
---
fs/kernfs/symlink.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index 08ccabd..774bada 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -63,6 +63,9 @@ static int kernfs_get_target_path(struct kernfs_node
if (base == kn)
break;
+ if ((s - path) + 3 >= PATH_MAX)
+ return -ENAMETOOLONG;
+
strcpy(s, "../");
s += 3;
base = base->parent;
@@ -79,7 +82,7 @@ static int kernfs_get_target_path(struct kernfs_node
if (len < 2)
return -EINVAL;
len--;
- if ((s - path) + len > PATH_MAX)
+ if ((s - path) + len >= PATH_MAX)
return -ENAMETOOLONG;
/* reverse fillup of target string from target to base */
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCHv3] Fix range checks in kernfs_get_target_path
2018-07-07 17:52 [PATCHv3] Fix range checks in kernfs_get_target_path Bernd Edlinger
@ 2018-08-26 10:55 ` Bernd Edlinger
2018-08-27 14:03 ` Tejun Heo
0 siblings, 1 reply; 3+ messages in thread
From: Bernd Edlinger @ 2018-08-26 10:55 UTC (permalink / raw)
To: Greg Kroah-Hartman, Tejun Heo, linux-kernel@vger.kernel.org
Ping...
Sorry, I had actually completely forgotten about this one.
On 07/07/18 19:52, Bernd Edlinger wrote:
> The terminating NUL byte is only there because the buffer is
> allocated with kzalloc(PAGE_SIZE, GFP_KERNEL), but since the
> range-check is off-by-one, and PAGE_SIZE==PATH_MAX, the
> returned string may not be zero-terminated if it is exactly
> PATH_MAX characters long. Furthermore also the initial loop
> may theoretically exceed PATH_MAX and cause a fault.
>
> Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
> ---
> fs/kernfs/symlink.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
> index 08ccabd..774bada 100644
> --- a/fs/kernfs/symlink.c
> +++ b/fs/kernfs/symlink.c
> @@ -63,6 +63,9 @@ static int kernfs_get_target_path(struct kernfs_node
> if (base == kn)
> break;
>
> + if ((s - path) + 3 >= PATH_MAX)
> + return -ENAMETOOLONG;
> +
> strcpy(s, "../");
> s += 3;
> base = base->parent;
> @@ -79,7 +82,7 @@ static int kernfs_get_target_path(struct kernfs_node
> if (len < 2)
> return -EINVAL;
> len--;
> - if ((s - path) + len > PATH_MAX)
> + if ((s - path) + len >= PATH_MAX)
> return -ENAMETOOLONG;
>
> /* reverse fillup of target string from target to base */
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCHv3] Fix range checks in kernfs_get_target_path
2018-08-26 10:55 ` Bernd Edlinger
@ 2018-08-27 14:03 ` Tejun Heo
0 siblings, 0 replies; 3+ messages in thread
From: Tejun Heo @ 2018-08-27 14:03 UTC (permalink / raw)
To: Bernd Edlinger; +Cc: Greg Kroah-Hartman, linux-kernel@vger.kernel.org
On Sun, Aug 26, 2018 at 10:55:24AM +0000, Bernd Edlinger wrote:
> Ping...
> Sorry, I had actually completely forgotten about this one.
>
> On 07/07/18 19:52, Bernd Edlinger wrote:
> > The terminating NUL byte is only there because the buffer is
> > allocated with kzalloc(PAGE_SIZE, GFP_KERNEL), but since the
> > range-check is off-by-one, and PAGE_SIZE==PATH_MAX, the
> > returned string may not be zero-terminated if it is exactly
> > PATH_MAX characters long. Furthermore also the initial loop
> > may theoretically exceed PATH_MAX and cause a fault.
> >
> > Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Acked-by: Tejun Heo <tj@kernel.org>
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-07-07 17:52 [PATCHv3] Fix range checks in kernfs_get_target_path Bernd Edlinger
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