On 1/10/17 1:42 PM, Darrick J. Wong wrote:
> xfs_db doesn't check the filesystem geometry when it's mounting, which
> means that garbage agcount values can cause OOMs when we try to allocate
> all the per-AG incore metadata. If we see geometry that looks
> suspicious, try to derive the actual AG geometry to avoid crashing the
> system. This should help with xfs/1301 fuzzing.
>
> Also fix up xfs_repair to use the min/max dblocks macros.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> db/init.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++------
> repair/sb.c | 7 +----
The repair change is an unrelated no-op cleanup, yes? Worth doing,
but in a second patch.
Ok, so now we do a whole bunch of tests and behind-your-back
fixups, but regardless of the problem we always issue the same
warning:
xfs_db: device fsfile AG geometry is insane. Using agcount=XX
... even if agcount wasn't the problem:
xfs_db> write -c blocksize 32768
Allowing write of corrupted data and bad CRC
blocksize = 32768
xfs_db> quit
[sandeen@sandeen xfsprogs]$ db/xfs_db -x fsfile
xfs_db: device fsfile AG geometry is insane. Using agcount=4.
That's confusing.
The whole point of xfs_db is to debug what is /on disk/ -
the above doesn't make it clear that it's not changed the on-disk
value. And it doesn't make it clear what was wrong, or what got changed.
But backing up - the /problem/ here is the OOM, right? That happens
for a very large agcount. We shouldn't be doing any more than that;
I don't really agree that your sanitize function should be fixing up
stuff behind the user's back. If it's broken, it's broken; let the
xfs_db wielding expert sort that out as long as xfs_db an be used to
do so.
But if the OOM means xfs_db can't start, then yeah, that's a problem.
What about sanitizing only the agcount, and saying something like:
xfs_db: device fsfile AG count is insane. Initializing only first $X
(where $X is based on your heuristics)
-Eric
> 2 files changed, 83 insertions(+), 15 deletions(-)
>
> diff --git a/db/init.c b/db/init.c
> index ec1e274..7e66d14 100644
> --- a/db/init.c
> +++ b/db/init.c
> @@ -51,13 +51,90 @@ usage(void)
> exit(1);
> }
>
> +/* Try to load an AG's superblock, no verifiers. */
> +static bool
> +load_sb(
> + struct xfs_mount *mp,
> + xfs_agnumber_t agno,
> + struct xfs_sb *sbp)
> +{
> + struct xfs_buf *bp;
> +
> + bp = libxfs_readbuf(mp->m_ddev_targp,
> + XFS_AG_DADDR(mp, agno, XFS_SB_DADDR),
> + 1 << (XFS_MAX_SECTORSIZE_LOG - BBSHIFT), 0, NULL);
> +
> + if (!bp || bp->b_error)
> + return false;
> +
> + /* copy SB from buffer to in-core, converting architecture as we go */
> + libxfs_sb_from_disk(sbp, XFS_BUF_TO_SBP(bp));
> + libxfs_putbuf(bp);
> + libxfs_purgebuf(bp);
> +
> + return true;
> +}
> +
> +/* If the geometry doesn't look sane, try to figure out the real geometry. */
> +static void
> +sanitize_geometry(
> + struct xfs_mount *mp,
> + struct xfs_sb *sbp)
> +{
> + struct xfs_sb sb;
> + xfs_agblock_t agblocks;
> +
> + /* If the geometry looks ok, we're done. */
> + if (sbp->sb_blocklog >= XFS_MIN_BLOCKSIZE_LOG &&
> + sbp->sb_blocklog <= XFS_MAX_BLOCKSIZE_LOG &&
> + sbp->sb_blocksize == (1 << sbp->sb_blocklog) &&
> + sbp->sb_dblocks * sbp->sb_blocksize <= x.dsize * x.dbsize &&
> + sbp->sb_dblocks <= XFS_MAX_DBLOCKS(sbp) &&
> + sbp->sb_dblocks >= XFS_MIN_DBLOCKS(sbp))
> + return;
> +
> + /* Check blocklog and blocksize */
> + if (sbp->sb_blocklog < XFS_MIN_BLOCKSIZE_LOG ||
> + sbp->sb_blocklog > XFS_MAX_BLOCKSIZE_LOG)
> + sbp->sb_blocklog = libxfs_log2_roundup(sbp->sb_blocksize);
> + if (sbp->sb_blocksize != (1 << sbp->sb_blocklog))
> + sbp->sb_blocksize = (1 << sbp->sb_blocksize);
> +
> + /* Clamp dblocks to the size of the device. */
> + if (sbp->sb_dblocks > x.dsize * x.dbsize / sbp->sb_blocksize)
> + sbp->sb_dblocks = x.dsize * x.dbsize / sbp->sb_blocksize;
> +
> + /* See if agblocks helps us find a superblock. */
> + mp->m_blkbb_log = sbp->sb_blocklog - BBSHIFT;
> + if (load_sb(mp, 1, &sb) && sb.sb_magicnum == XFS_SB_MAGIC) {
> + sbp->sb_agcount = sbp->sb_dblocks / sbp->sb_agblocks;
> + goto out;
> + }
> +
> + /* See if agcount helps us find a superblock. */
> + agblocks = sbp->sb_agblocks;
> + sbp->sb_agblocks = sbp->sb_dblocks / sbp->sb_agcount;
> + if (sbp->sb_agblocks != 0 &&
> + load_sb(mp, 1, &sb) &&
> + sb.sb_magicnum == XFS_SB_MAGIC) {
> + goto out;
> + }
> +
> + /* Both are nuts, assume 1 AG. */
> + sbp->sb_agblocks = agblocks;
> + sbp->sb_agcount = 1;
> +out:
> + fprintf(stderr,
> + _("%s: device %s AG geometry is insane. Using agcount=%u.\n"),
> + progname, fsdevice, sbp->sb_agcount);
> +}
> +
> void
> init(
> int argc,
> char **argv)
> {
> struct xfs_sb *sbp;
> - struct xfs_buf *bp;
> int c;
>
> setlocale(LC_ALL, "");
> @@ -124,20 +201,12 @@ init(
> */
> memset(&xmount, 0, sizeof(struct xfs_mount));
> libxfs_buftarg_init(&xmount, x.ddev, x.logdev, x.rtdev);
> - bp = libxfs_readbuf(xmount.m_ddev_targp, XFS_SB_DADDR,
> - 1 << (XFS_MAX_SECTORSIZE_LOG - BBSHIFT), 0, NULL);
> -
> - if (!bp || bp->b_error) {
> + if (!load_sb(&xmount, 0, &xmount.m_sb)) {
> fprintf(stderr, _("%s: %s is invalid (cannot read first 512 "
> "bytes)\n"), progname, fsdevice);
> exit(1);
> }
>
> - /* copy SB from buffer to in-core, converting architecture as we go */
> - libxfs_sb_from_disk(&xmount.m_sb, XFS_BUF_TO_SBP(bp));
> - libxfs_putbuf(bp);
> - libxfs_purgebuf(bp);
> -
> sbp = &xmount.m_sb;
> if (sbp->sb_magicnum != XFS_SB_MAGIC) {
> fprintf(stderr, _("%s: %s is not a valid XFS filesystem (unexpected SB magic number 0x%08x)\n"),
> @@ -148,6 +217,8 @@ init(
> }
> }
>
> + sanitize_geometry(&xmount, sbp);
> +
> mp = libxfs_mount(&xmount, sbp, x.ddev, x.logdev, x.rtdev,
> LIBXFS_MOUNT_DEBUGGER);
> if (!mp) {
> diff --git a/repair/sb.c b/repair/sb.c
> index 1b352e8..e108613 100644
> --- a/repair/sb.c
> +++ b/repair/sb.c
> @@ -398,11 +398,8 @@ verify_sb(char *sb_buf, xfs_sb_t *sb, int is_primary_sb)
> /* sanity check ag count, size fields against data size field */
>
> if (sb->sb_dblocks == 0 ||
> - sb->sb_dblocks >
> - ((__uint64_t)sb->sb_agcount * sb->sb_agblocks) ||
> - sb->sb_dblocks <
> - ((__uint64_t)(sb->sb_agcount - 1) * sb->sb_agblocks
> - + XFS_MIN_AG_BLOCKS))
> + sb->sb_dblocks > XFS_MAX_DBLOCKS(sb) ||
> + sb->sb_dblocks < XFS_MIN_DBLOCKS(sb))
> return(XR_BAD_FS_SIZE_DATA);
>
> if (sb->sb_agblklog != (__uint8_t)libxfs_log2_roundup(sb->sb_agblocks))
> --
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