xfs: underflow bug in xfs_attrlist_by_handle()

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>

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 4d613401a5e056a08dd2f8b21b77833bfe14cbc6..33ad9a77791f7ebbf3f8762e0c9df1af637c5328 100644 (file)
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -442,7 +442,8 @@ 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 --cc fs/xfs/xfs_ioctl32.c
Simple merge