Commit 0ddc5154 authored Oct 14, 2020 by Anant Thazhemadam Committed by Andreas Gruenbacher Oct 15, 2020

gfs2: add validation checks for size of superblock



In gfs2_check_sb(), no validation checks are performed with regards to
the size of the superblock.
syzkaller detected a slab-out-of-bounds bug that was primarily caused
because the block size for a superblock was set to zero.
A valid size for a superblock is a power of 2 between 512 and PAGE_SIZE.
Performing validation checks and ensuring that the size of the superblock
is valid fixes this bug.

Reported-by:  <syzbot+af90d47a37376844e731@syzkaller.appspotmail.com>
Tested-by:  <syzbot+af90d47a37376844e731@syzkaller.appspotmail.com>
Suggested-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
[Minor code reordering.]
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

parent c2a04b02

fs/gfs2/ops_fstype.c

+11 −7

Original line number	Diff line number	Diff line
		@@ -169,17 +169,21 @@ static int gfs2_check_sb(struct gfs2_sbd *sdp, int silent)
		return -EINVAL;
		}

		/* If format numbers match exactly, we're done. */

		if (sb->sb_fs_format == GFS2_FORMAT_FS &&
		sb->sb_multihost_format == GFS2_FORMAT_MULTI)
		return 0;

		if (sb->sb_fs_format != GFS2_FORMAT_FS \|\|
		sb->sb_multihost_format != GFS2_FORMAT_MULTI) {
		fs_warn(sdp, "Unknown on-disk format, unable to mount\n");
		return -EINVAL;
		}

		if (sb->sb_bsize < 512 \|\| sb->sb_bsize > PAGE_SIZE \|\|
		(sb->sb_bsize & (sb->sb_bsize - 1))) {
		pr_warn("Invalid superblock size\n");
		return -EINVAL;
		}

		return 0;
		}

		static void end_bio_io_page(struct bio *bio)
		{
		struct page *page = bio->bi_private;

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