On Mon, Jan 15, 2018 at 12:03:13PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Currently, we don't check sb_agblocks or sb_agblklog when we validate
> the superblock, which means that we can fuzz garbage values into those
> values and the mount succeeds. This leads to all sorts of UBSAN
> warnings in xfs/350 since we can then coerce other parts of xfs into
> shifting by ridiculously large values.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> v2: simplify ag min/max size definitions
> ---
> fs/xfs/libxfs/xfs_fs.h | 7 +++++++
> fs/xfs/libxfs/xfs_sb.c | 3 +++
> 2 files changed, 10 insertions(+)
>
> diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
> index fc4386a..3ab1870 100644
> --- a/fs/xfs/libxfs/xfs_fs.h
> +++ b/fs/xfs/libxfs/xfs_fs.h
> @@ -233,6 +233,13 @@ typedef struct xfs_fsop_resblks {
> #define XFS_MAX_LOG_BLOCKS (1024 * 1024ULL)
> #define XFS_MIN_LOG_BYTES (10 * 1024 * 1024ULL)
>
> +/*
> + * Limits on sb_agblocks/sb_agblklog -- mkfs won't format AGs smaller than
> + * 16MB or larger than 1TB.
> + */
> +#define XFS_AG_MIN_BYTES (1ULL << 24) /* 16 MB */
> +#define XFS_AG_MAX_BYTES (1ULL << 40) /* 1 TB */
Sure, but....
> +
> /* keep the maximum size under 2^31 by a small amount */
> #define XFS_MAX_LOG_BYTES \
> ((2 * 1024 * 1024 * 1024ULL) - XFS_MIN_LOG_BYTES)
> diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
> index 08e44a0..bdb4f74 100644
> --- a/fs/xfs/libxfs/xfs_sb.c
> +++ b/fs/xfs/libxfs/xfs_sb.c
> @@ -253,6 +253,9 @@ xfs_mount_validate_sb(
> sbp->sb_inodesize != (1 << sbp->sb_inodelog) ||
> sbp->sb_logsunit > XLOG_MAX_RECORD_BSIZE ||
> sbp->sb_inopblock != howmany(sbp->sb_blocksize,sbp->sb_inodesize) ||
> + XFS_FSB_TO_B(mp, sbp->sb_agblocks) < XFS_AG_MIN_BYTES ||
> + XFS_FSB_TO_B(mp, sbp->sb_agblocks) > XFS_AG_MAX_BYTES ||
.... this really needs to be checked against sb_dblocks /
sb_agcount. i.e. check against current filesystem size and geometry,
not against the theoretical maximum.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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