From: Anant Thazhemadam anant.thazhemadam@gmail.com
stable inclusion from linux-4.19.155 commit 6a253f385a2dc9f6a5a1da828e0e9e07f6f9d9b9
--------------------------------
[ Upstream commit 0ddc5154b24c96f20e94d653b0a814438de6032b ]
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 Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/gfs2/ops_fstype.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c index 9448c8461e57..17001f4e9f84 100644 --- a/fs/gfs2/ops_fstype.c +++ b/fs/gfs2/ops_fstype.c @@ -161,15 +161,19 @@ 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; + }
- fs_warn(sdp, "Unknown on-disk format, unable to mount\n"); + 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 -EINVAL; + return 0; }
static void end_bio_io_page(struct bio *bio)