xfs: underflow bug in xfs_attrlist_by_handle()

commit 31978b5cc66b8ba8a7e8eef60b12395d41b7b890 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 91f8ff547ab3771f3df70e631aaf0804256f8eba..6a6c1fdb789226114514f564473faa5aa97e30e8 100644 (file)
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -400,7 +400,8 @@ 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/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
index a849a5473aff41ec61dcb0770cc3251fab318206..745ea4ea98ab901590dcf4ec1df91b19bf129f54 100644 (file)
--- a/fs/xfs/xfs_ioctl32.c
+++ b/fs/xfs/xfs_ioctl32.c
@@ -361,7 +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)
+       if (al_hreq.buflen < sizeof(struct attrlist) ||
+           al_hreq.buflen > XATTR_LIST_MAX)
                return -XFS_ERROR(EINVAL);
 
        /*