From: Darrick J. Wong Date: Tue, 27 Aug 2019 00:06:01 +0000 (-0700) Subject: xfs: fix maxicount division by zero error X-Git-Tag: v5.4-rc1~120^2~38 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c94613feefd7714ad0d03a1914632c15782114ff;p=thirdparty%2Fkernel%2Flinux.git xfs: fix maxicount division by zero error In xfs_ialloc_setup_geometry, it's possible for a malicious/corrupt fs image to set an unreasonably large value for sb_inopblog which will cause ialloc_blks to be zero. If sb_imax_pct is also set, this results in a division by zero error in the second do_div call. Therefore, force maxicount to zero if ialloc_blks is zero. Note that the kernel metadata verifiers will catch the garbage inopblog value and abort the fs mount long before it tries to set up the inode geometry; this is needed to avoid a crash in xfs_db while setting up the xfs_mount structure. Found by fuzzing sb_inopblog to 122 in xfs/350. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner Reviewed-by: Carlos Maiolino --- diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c index 04377ab758630..588d446130944 100644 --- a/fs/xfs/libxfs/xfs_ialloc.c +++ b/fs/xfs/libxfs/xfs_ialloc.c @@ -2787,8 +2787,13 @@ xfs_ialloc_setup_geometry( igeo->inobt_maxlevels = xfs_btree_compute_maxlevels(igeo->inobt_mnr, inodes); - /* Set the maximum inode count for this filesystem. */ - if (sbp->sb_imax_pct) { + /* + * Set the maximum inode count for this filesystem, being careful not + * to use obviously garbage sb_inopblog/sb_inopblock values. Regular + * users should never get here due to failing sb verification, but + * certain users (xfs_db) need to be usable even with corrupt metadata. + */ + if (sbp->sb_imax_pct && igeo->ialloc_blks) { /* * Make sure the maximum inode count is a multiple * of the units we allocate inodes in.