On Tue, Jan 16, 2018 at 05:20:22PM -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.
>
> Once we've validated agblocks, make sure the agcount makes sense.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> v3: also check that dblocks/agcount/agblocks make sense
> v2: simplify ag min/max size definitions
> ---
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> fs/xfs/libxfs/xfs_fs.h | 7 +++++++
> fs/xfs/libxfs/xfs_sb.c | 14 ++++++++++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
> index fc4386a..1de8555 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_MIN_AG_BYTES (1ULL << 24) /* 16 MB */
> +#define XFS_MAX_AG_BYTES (1ULL << 40) /* 1 TB */
> +
> /* 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..e2b82d7 100644
> --- a/fs/xfs/libxfs/xfs_sb.c
> +++ b/fs/xfs/libxfs/xfs_sb.c
> @@ -119,6 +119,9 @@ xfs_mount_validate_sb(
> bool check_inprogress,
> bool check_version)
> {
> + u32 agcount = 0;
> + u32 rem;
> +
> if (sbp->sb_magicnum != XFS_SB_MAGIC) {
> xfs_warn(mp, "bad magic number");
> return -EWRONGFS;
> @@ -229,6 +232,13 @@ xfs_mount_validate_sb(
> return -EINVAL;
> }
>
> + /* Compute agcount for this number of dblocks and agblocks */
> + if (sbp->sb_agblocks) {
> + agcount = div_u64_rem(sbp->sb_dblocks, sbp->sb_agblocks, &rem);
> + if (rem)
> + agcount++;
> + }
> +
> /*
> * More sanity checking. Most of these were stolen directly from
> * xfs_repair.
> @@ -253,6 +263,10 @@ 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_MIN_AG_BYTES ||
> + XFS_FSB_TO_B(mp, sbp->sb_agblocks) > XFS_MAX_AG_BYTES ||
> + sbp->sb_agblklog != xfs_highbit32(sbp->sb_agblocks - 1) + 1 ||
> + agcount == 0 || agcount != sbp->sb_agcount ||
> (sbp->sb_blocklog - sbp->sb_inodelog != sbp->sb_inopblog) ||
> (sbp->sb_rextsize * sbp->sb_blocksize > XFS_MAX_RTEXTSIZE) ||
> (sbp->sb_rextsize * sbp->sb_blocksize < XFS_MIN_RTEXTSIZE) ||
> --
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