Re: [ 137/143] xfs: underflow bug in xfs_attrlist_by_handle()

Luis Henriques
2014-05-13T11:08:19Z

On Mon, May 12, 2014 at 02:34:17AM +0200, Willy Tarreau wrote:
> 2.6.32-longterm review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Dan Carpenter <dan.carpenter@oracle.com>
>
> If we allocate less than sizeof(struct attrlist) then we end up
> corrupting memory or doing a ZERO_PTR_SIZE dereference.
>
> This can only be triggered with CAP_SYS_ADMIN.
>
> Reported-by: Nico Golde <nico@ngolde.de>
> Reported-by: Fabian Yamaguchi <fabs@goesec.de>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> Reviewed-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Ben Myers <bpm@sgi.com>
>
> (cherry picked from commit 071c529eb672648ee8ca3f90944bcbcc730b4c06)
> [dannf: backported to Debian's 2.6.32]
> Signed-off-by: Willy Tarreau <w@1wt.eu>
> ---
> fs/xfs/linux-2.6/xfs_ioctl.c | 3 ++-
> fs/xfs/linux-2.6/xfs_ioctl32.c | 4 ++--
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/xfs/linux-2.6/xfs_ioctl.c b/fs/xfs/linux-2.6/xfs_ioctl.c
> index 942362f..5663351 100644
> --- a/fs/xfs/linux-2.6/xfs_ioctl.c
> +++ b/fs/xfs/linux-2.6/xfs_ioctl.c
> @@ -410,7 +410,8 @@ xfs_attrlist_by_handle(
> return -XFS_ERROR(EPERM);
> if (copy_from_user(&al_hreq, arg, sizeof(xfs_fsop_attrlist_handlereq_t)))
> return -XFS_ERROR(EFAULT);
> - if (al_hreq.buflen > XATTR_LIST_MAX)
> + if (al_hreq.buflen < sizeof(struct attrlist) ||
> + al_hreq.buflen > XATTR_LIST_MAX)
> return -XFS_ERROR(EINVAL);
>
> /*
> diff --git a/fs/xfs/linux-2.6/xfs_ioctl32.c b/fs/xfs/linux-2.6/xfs_ioctl32.c
> index bad485a..782d03d 100644
> --- a/fs/xfs/linux-2.6/xfs_ioctl32.c
> +++ b/fs/xfs/linux-2.6/xfs_ioctl32.c
> @@ -361,8 +361,8 @@ xfs_compat_attrlist_by_handle(
> if (copy_from_user(&al_hreq, arg,
> sizeof(compat_xfs_fsop_attrlist_handlereq_t)))
> return -XFS_ERROR(EFAULT);
> - if (al_hreq.buflen > XATTR_LIST_MAX)
> - return -XFS_ERROR(EINVAL);

Am I missing something or was the above return statement deleted by
mistake?

Cheers,
--
Luís

> + if (al_hreq.buflen < sizeof(struct attrlist) ||
> + al_hreq.buflen > XATTR_LIST_MAX)
>
> /*
> * Reject flags, only allow namespaces.
> --
> 1.7.12.2.21.g234cd45.dirty
>
>
>
> --
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