From 556b8883cfac3d3203557e161ea8005f8b5479b2 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Fri, 6 Jun 2014 16:00:43 +1000 Subject: [PATCH] xfs: xfs_readsb needs to check for magic numbers Commit daba542 ("xfs: skip verification on initial "guess" superblock read") dropped the use of a verifier for the initial superblock read so we can probe the sector size of the filesystem stored in the superblock. It, however, now fails to validate that what was read initially is actually an XFS superblock and hence will fail the sector size check and return ENOSYS. This causes probe-based mounts to fail because it expects XFS to return EINVAL when it doesn't recognise the superblock format. cc: Reported-by: Plamen Petrov Tested-by: Plamen Petrov Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Dave Chinner --- fs/xfs/xfs_mount.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c index 944f3d9456a8..a9e29ea37620 100644 --- a/fs/xfs/xfs_mount.c +++ b/fs/xfs/xfs_mount.c @@ -323,8 +323,19 @@ reread: /* * Initialize the mount structure from the superblock. */ - xfs_sb_from_disk(&mp->m_sb, XFS_BUF_TO_SBP(bp)); - xfs_sb_quota_from_disk(&mp->m_sb); + xfs_sb_from_disk(sbp, XFS_BUF_TO_SBP(bp)); + xfs_sb_quota_from_disk(sbp); + + /* + * If we haven't validated the superblock, do so now before we try + * to check the sector size and reread the superblock appropriately. + */ + if (sbp->sb_magicnum != XFS_SB_MAGIC) { + if (loud) + xfs_warn(mp, "Invalid superblock magic number"); + error = EINVAL; + goto release_buf; + } /* * We must be able to do sector-sized and sector-aligned IO. @@ -337,11 +348,11 @@ reread: goto release_buf; } - /* - * Re-read the superblock so the buffer is correctly sized, - * and properly verified. - */ if (buf_ops == NULL) { + /* + * Re-read the superblock so the buffer is correctly sized, + * and properly verified. + */ xfs_buf_relse(bp); sector_size = sbp->sb_sectsize; buf_ops = loud ? &xfs_sb_buf_ops : &xfs_sb_quiet_buf_ops; -- 2.39.5