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authorDarrick J. Wong <djwong@kernel.org>2023-06-29 19:15:45 +0200
committerDarrick J. Wong <djwong@kernel.org>2023-07-03 18:48:17 +0200
commit2d7d1e7ea321b0b2810eb00183e21332ee9c4b6f (patch)
treee00f7799bc0b522fc99e9d3371d0e9f5d83c5475 /fs/xfs/libxfs/xfs_alloc.c
parentxfs: fix the calculation for "end" and "length" (diff)
downloadlinux-2d7d1e7ea321b0b2810eb00183e21332ee9c4b6f.tar.xz
linux-2d7d1e7ea321b0b2810eb00183e21332ee9c4b6f.zip
xfs: AGI length should be bounds checked
Similar to the recent patch strengthening the AGF agf_length verification, the AGI verifier does not check that the AGI length field is within known good bounds. This isn't currently checked by runtime kernel code, yet we assume in many places that it is correct and verify other metadata against it. Add length verification to the AGI verifier. Just like the AGF length checking, the length of the AGI must be equal to the size of the AG specified in the superblock, unless it is the last AG in the filesystem. In that case, it must be less than or equal to sb->sb_agblocks and greater than XFS_MIN_AG_BLOCKS, which is the smallest AG a growfs operation will allow to exist. There's only one place in the filesystem that actually uses agi_length, but let's not leave it vulnerable to the same weird nonsense that generates syzbot bugs, eh? Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Dave Chinner <dchinner@redhat.com>
Diffstat (limited to 'fs/xfs/libxfs/xfs_alloc.c')
-rw-r--r--fs/xfs/libxfs/xfs_alloc.c72
1 files changed, 46 insertions, 26 deletions
diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 200c460a3c7a..3069194527dd 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -2957,6 +2957,47 @@ xfs_alloc_put_freelist(
}
/*
+ * Check that this AGF/AGI header's sequence number and length matches the AG
+ * number and size in fsblocks.
+ */
+xfs_failaddr_t
+xfs_validate_ag_length(
+ struct xfs_buf *bp,
+ uint32_t seqno,
+ uint32_t length)
+{
+ struct xfs_mount *mp = bp->b_mount;
+ /*
+ * During growfs operations, the perag is not fully initialised,
+ * so we can't use it for any useful checking. growfs ensures we can't
+ * use it by using uncached buffers that don't have the perag attached
+ * so we can detect and avoid this problem.
+ */
+ if (bp->b_pag && seqno != bp->b_pag->pag_agno)
+ return __this_address;
+
+ /*
+ * Only the last AG in the filesystem is allowed to be shorter
+ * than the AG size recorded in the superblock.
+ */
+ if (length != mp->m_sb.sb_agblocks) {
+ /*
+ * During growfs, the new last AG can get here before we
+ * have updated the superblock. Give it a pass on the seqno
+ * check.
+ */
+ if (bp->b_pag && seqno != mp->m_sb.sb_agcount - 1)
+ return __this_address;
+ if (length < XFS_MIN_AG_BLOCKS)
+ return __this_address;
+ if (length > mp->m_sb.sb_agblocks)
+ return __this_address;
+ }
+
+ return NULL;
+}
+
+/*
* Verify the AGF is consistent.
*
* We do not verify the AGFL indexes in the AGF are fully consistent here
@@ -2975,6 +3016,8 @@ xfs_agf_verify(
{
struct xfs_mount *mp = bp->b_mount;
struct xfs_agf *agf = bp->b_addr;
+ xfs_failaddr_t fa;
+ uint32_t agf_seqno = be32_to_cpu(agf->agf_seqno);
uint32_t agf_length = be32_to_cpu(agf->agf_length);
if (xfs_has_crc(mp)) {
@@ -2993,33 +3036,10 @@ xfs_agf_verify(
/*
* Both agf_seqno and agf_length need to validated before anything else
* block number related in the AGF or AGFL can be checked.
- *
- * During growfs operations, the perag is not fully initialised,
- * so we can't use it for any useful checking. growfs ensures we can't
- * use it by using uncached buffers that don't have the perag attached
- * so we can detect and avoid this problem.
- */
- if (bp->b_pag && be32_to_cpu(agf->agf_seqno) != bp->b_pag->pag_agno)
- return __this_address;
-
- /*
- * Only the last AGF in the filesytsem is allowed to be shorter
- * than the AG size recorded in the superblock.
*/
- if (agf_length != mp->m_sb.sb_agblocks) {
- /*
- * During growfs, the new last AGF can get here before we
- * have updated the superblock. Give it a pass on the seqno
- * check.
- */
- if (bp->b_pag &&
- be32_to_cpu(agf->agf_seqno) != mp->m_sb.sb_agcount - 1)
- return __this_address;
- if (agf_length < XFS_MIN_AG_BLOCKS)
- return __this_address;
- if (agf_length > mp->m_sb.sb_agblocks)
- return __this_address;
- }
+ fa = xfs_validate_ag_length(bp, agf_seqno, agf_length);
+ if (fa)
+ return fa;
if (be32_to_cpu(agf->agf_flfirst) >= xfs_agfl_size(mp))
return __this_address;