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SubjectRe: [PATCHv3] Fix range checks in kernfs_get_target_path
Date
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 */
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