When xfs_readsb() does the very first read of the superblock,
it makes a guess at the length of the buffer, based on the
sector size of the underlying storage. This may or may
not match the filesystem sector size in sb_sectsize, so
we can't i.e. do a CRC check on it; it might be too short.
In fact, mounting a filesystem with sb_sectsize larger
than the device sector size will cause a mount failure
if CRCs are enabled, because we are checksumming a length
which exceeds the buffer passed to it.
So always read twice; the first time we read with NULL
buffer ops to skip verification; then set the proper
read length, hook up the proper verifier, and give it
another go.
Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---
V3: Go back to always reading twice, to avoid the need for
duplicating the code that handles verifier errors.
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 02df7b4..f96c056 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -282,22 +282,29 @@ xfs_readsb(
struct xfs_sb *sbp = &mp->m_sb;
int error;
int loud = !(flags & XFS_MFSI_QUIET);
+ const struct xfs_buf_ops *buf_ops;
ASSERT(mp->m_sb_bp == NULL);
ASSERT(mp->m_ddev_targp != NULL);
/*
+ * For the initial read, we must guess at the sector
+ * size based on the block device. It's enough to
+ * get the sb_sectsize out of the superblock and
+ * then we can reread with the proper length.
+ * We don't verify it yet, because it may not be complete.
+ */
+ sector_size = xfs_getsize_buftarg(mp->m_ddev_targp);
+ buf_ops = NULL;
+
+ /*
* Allocate a (locked) buffer to hold the superblock.
* This will be kept around at all times to optimize
* access to the superblock.
*/
- sector_size = xfs_getsize_buftarg(mp->m_ddev_targp);
-
reread:
bp = xfs_buf_read_uncached(mp->m_ddev_targp, XFS_SB_DADDR,
- BTOBB(sector_size), 0,
- loud ? &xfs_sb_buf_ops
- : &xfs_sb_quiet_buf_ops);
+ BTOBB(sector_size), 0, buf_ops);
if (!bp) {
if (loud)
xfs_warn(mp, "SB buffer read failed");
@@ -328,12 +335,13 @@ reread:
}
/*
- * If device sector size is smaller than the superblock size,
- * re-read the superblock so the buffer is correctly sized.
+ * Re-read the superblock so the buffer is correctly sized,
+ * and properly verified.
*/
- if (sector_size < sbp->sb_sectsize) {
+ if (buf_ops == NULL) {
xfs_buf_relse(bp);
sector_size = sbp->sb_sectsize;
+ buf_ops = loud ? &xfs_sb_buf_ops : &xfs_sb_quiet_buf_ops;
goto reread;
}
diff --git a/fs/xfs/xfs_sb.c b/fs/xfs/xfs_sb.c
index 5071ccb..1b0b503 100644
--- a/fs/xfs/xfs_sb.c
+++ b/fs/xfs/xfs_sb.c
@@ -644,7 +644,6 @@ xfs_sb_quiet_read_verify(
{
struct xfs_dsb *dsb = XFS_BUF_TO_SBP(bp);
-
if (dsb->sb_magicnum == cpu_to_be32(XFS_SB_MAGIC)) {
/* XFS filesystem, verify noisily! */
xfs_sb_read_verify(bp);
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