[PATCH] xfs: bound inode fork length against the fork size during log recovery

[Aldo Ariel Panzardo <qwe.aldo@gmail.com>]

xlog_recover_inode_commit_pass2() copies an inode log item's data/attr
fork region into the inode buffer using the on-log region length without
bounding it against the fork capacity, e.g.:

	len = item->ri_buf[2].iov_len;
	memcpy(XFS_DFORK_DPTR(dip), src, len);

The only guard is an ASSERT, which is a no-op on production kernels
(CONFIG_XFS_DEBUG off), and xfs_dinode_verify() runs only after the copy.
A crafted image with a dirty log can therefore drive a heap out-of-bounds
write at mount time. The XFS_ILOG_DBROOT sibling already passes
XFS_DFORK_DSIZE as a bound; the DDATA/DEXT and ADATA/AEXT memcpy paths
did not.

Reject the log item with -EFSCORRUPTED when the region length exceeds the
destination fork size.

Fixes: 658fa68b6f34 ("xfs: refactor log recovery inode item dispatch for pass2 commit functions")
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@gmail.com>
---
 fs/xfs/xfs_inode_item_recover.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_inode_item_recover.c b/fs/xfs/xfs_inode_item_recover.c
index 169a8fe3bf0a..388d3a8dbd31 100644
--- a/fs/xfs/xfs_inode_item_recover.c
+++ b/fs/xfs/xfs_inode_item_recover.c
@@ -510,6 +510,10 @@ xlog_recover_inode_commit_pass2(
 	switch (fields & XFS_ILOG_DFORK) {
 	case XFS_ILOG_DDATA:
 	case XFS_ILOG_DEXT:
+		if (len > XFS_DFORK_DSIZE(dip, mp)) {
+			error = -EFSCORRUPTED;
+			goto out_release;
+		}
 		memcpy(XFS_DFORK_DPTR(dip), src, len);
 		break;
 
@@ -545,8 +549,11 @@ xlog_recover_inode_commit_pass2(
 		switch (in_f->ilf_fields & XFS_ILOG_AFORK) {
 		case XFS_ILOG_ADATA:
 		case XFS_ILOG_AEXT:
+			if (len > XFS_DFORK_ASIZE(dip, mp)) {
+				error = -EFSCORRUPTED;
+				goto out_release;
+			}
 			dest = XFS_DFORK_APTR(dip);
-			ASSERT(len <= XFS_DFORK_ASIZE(dip, mp));
 			memcpy(dest, src, len);
 			break;
 
-- 
2.43.0