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.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
v2: Only modify sb_ag{blocks,count} if they seem insane -- use local
variables to avoid screwing up the rest of the metadata.
v3: Suggest a possible agcount value, but always restrict to 1 AG.
---
db/init.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 85 insertions(+), 10 deletions(-)
diff --git a/db/init.c b/db/init.c
index ec1e274..43a9409 100644
--- a/db/init.c
+++ b/db/init.c
@@ -51,13 +51,94 @@ usage(void)
exit(1);
}
+/* Try to load a superblock for the given agno, 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 agcount doesn't look sane, suggest a real agcount to the user,
+ * and pretend agcount = 1 to avoid OOMing libxfs_initialize_perag.
+ */
+static void
+sanitize_geometry(
+ struct xfs_mount *mp,
+ struct xfs_sb *sbp)
+{
+ struct xfs_sb sb;
+ unsigned int blocklog;
+ unsigned int blocksize;
+ unsigned int agblocks;
+ unsigned long long dblocks;
+
+ /* 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 */
+ blocklog = sbp->sb_blocklog;
+ blocksize = sbp->sb_blocksize;
+ if (blocklog < XFS_MIN_BLOCKSIZE_LOG ||
+ blocklog > XFS_MAX_BLOCKSIZE_LOG)
+ blocklog = libxfs_log2_roundup(blocksize);
+ if (blocksize != (1 << blocklog))
+ blocksize = (1 << blocksize);
+
+ /* Clamp dblocks to the size of the device. */
+ dblocks = sbp->sb_dblocks;
+ if (dblocks > x.dsize * x.dbsize / blocksize)
+ dblocks = x.dsize * x.dbsize / blocksize;
+
+ /*
+ * See if agblocks helps us find a superblock.
+ * blkbb_log is later (re)set by libxfs_mount.
+ */
+ mp->m_blkbb_log = blocklog - BBSHIFT;
+ if (sbp->sb_agblocks > 0 && sbp->sb_agblocks <= MAXEXTNUM &&
+ load_sb(mp, 1, &sb) && sb.sb_magicnum == XFS_SB_MAGIC) {
+ fprintf(stderr,
+_("%s: device %s AG count is insane, but could be %u. Limiting reads to AG 0.\n"),
+ progname, fsdevice, dblocks / sbp->sb_agblocks);
+ } else {
+ fprintf(stderr,
+_("%s: device %s AG count is insane. Limiting reads to AG 0.\n"),
+ progname, fsdevice);
+ }
+
+ /* Assume 1 AG to avoid OOM. */
+ sbp->sb_agcount = 1;
+}
+
void
init(
int argc,
char **argv)
{
struct xfs_sb *sbp;
- struct xfs_buf *bp;
int c;
setlocale(LC_ALL, "");
@@ -124,20 +205,12 @@ 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 +221,8 @@ init(
}
}
+ sanitize_geometry(&xmount, sbp);
+
mp = libxfs_mount(&xmount, sbp, x.ddev, x.logdev, x.rtdev,
LIBXFS_MOUNT_DEBUGGER);
if (!mp) {
--
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