xfs: convert flex-array declarations in struct xfs_attrlist*

As of 6.5-rc1, UBSAN trips over the attrlist ioctl definitions using an
array length of 1 to pretend to be a flex array.  Kernel compilers have
to support unbounded array declarations, so let's correct this.  This
may cause friction with userspace header declarations, but suck is life.

================================================================================
UBSAN: array-index-out-of-bounds in fs/xfs/xfs_ioctl.c:345:18
index 1 is out of range for type '__s32 [1]'
Call Trace:
 <TASK>
 dump_stack_lvl+0x33/0x50
 __ubsan_handle_out_of_bounds+0x9c/0xd0
 xfs_ioc_attr_put_listent+0x413/0x420 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
 xfs_attr_list_ilocked+0x170/0x850 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
 xfs_attr_list+0xb7/0x120 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
 xfs_ioc_attr_list+0x13b/0x2e0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
 xfs_attrlist_by_handle+0xab/0x120 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
 xfs_file_ioctl+0x1ff/0x15e0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09]
 vfs_ioctl+0x1f/0x60

The kernel and xfsprogs code that uses these structures will not have
problems, but the long tail of external user programs might.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>

diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
index 9c60ebb..2cbf9ea 100644 (file)
--- a/fs/xfs/libxfs/xfs_fs.h
+++ b/fs/xfs/libxfs/xfs_fs.h
@@ -592,12 +592,12 @@ typedef struct xfs_attrlist_cursor {
 struct xfs_attrlist {
        __s32   al_count;       /* number of entries in attrlist */
        __s32   al_more;        /* T/F: more attrs (do call again) */
-       __s32   al_offset[1];   /* byte offsets of attrs [var-sized] */
+       __s32   al_offset[];    /* byte offsets of attrs [var-sized] */
 };
 
 struct xfs_attrlist_ent {      /* data from attr_list() */
        __u32   a_valuelen;     /* number bytes in value of attr */
-       char    a_name[1];      /* attr name (NULL terminated) */
+       char    a_name[];       /* attr name (NULL terminated) */
 };
 
 typedef struct xfs_fsop_attrlist_handlereq {