[PATCH 7/7] xfs: sanity check attr fork size

Christoph Hellwig
2009-01-09T22:13:03Z

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Recently we have quite a few kerneloops reports about dereferencing a NULL
if_data in the attribute fork. From looking over the code this can only
happen if we pass a 0 size argument to xfs_iformat_local. This implies some
sort of corruption and in fact the only mailinglist report about this from
earlier this year was after a powerfail presumably on a system with write
cache and without barriers.

Add a quick sanity check for the attr fork size in xfs_iformat to catch
these early and without an oops.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <david@fromorbit.com>

Index: linux-2.6/fs/xfs/xfs_inode.c
===================================================================
--- linux-2.6.orig/fs/xfs/xfs_inode.c 2009-01-04 17:35:11.955671640 +0100
+++ linux-2.6/fs/xfs/xfs_inode.c 2009-01-04 17:38:04.643673527 +0100
@@ -424,6 +424,19 @@ xfs_iformat(
case XFS_DINODE_FMT_LOCAL:
atp = (xfs_attr_shortform_t *)XFS_DFORK_APTR(dip);
size = be16_to_cpu(atp->hdr.totsize);
+
+ if (unlikely(size < sizeof(struct xfs_attr_sf_hdr))) {
+ xfs_fs_repair_cmn_err(CE_WARN, ip->i_mount,
+ "corrupt inode %Lu "
+ "(bad attr fork size %Ld).",
+ (unsigned long long) ip->i_ino,
+ (long long) size);
+ XFS_CORRUPTION_ERROR("xfs_iformat(8)",
+ XFS_ERRLEVEL_LOW,
+ ip->i_mount, dip);
+ return XFS_ERROR(EFSCORRUPTED);
+ }
+
error = xfs_iformat_local(ip, dip, XFS_ATTR_FORK, size);
break;