From: Andrew Price <anprice@redhat.com> stable inclusion from stable-v4.19.267 commit 15c83fa0fd659dd9fbdc940a560b61236e876a80 category: bugfix bugzilla: 190603 CVE: CVE-2022-49769 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 670f8ce56dd0632dc29a0322e188cc73ce3c6b92 upstream. Fuzzers like to scribble over sb_bsize_shift but in reality it's very unlikely that this field would be corrupted on its own. Nevertheless it should be checked to avoid the possibility of messy mount errors due to bad calculations. It's always a fixed value based on the block size so we can just check that it's the expected value. Tested with: mkfs.gfs2 -O -p lock_nolock /dev/vdb for i in 0 -1 64 65 32 33; do gfs2_edit -p sb field sb_bsize_shift $i /dev/vdb mount /dev/vdb /mnt/test && umount /mnt/test done Before this patch we get a withdraw after [ 76.413681] gfs2: fsid=loop0.0: fatal: invalid metadata block [ 76.413681] bh = 19 (type: exp=5, found=4) [ 76.413681] function = gfs2_meta_buffer, file = fs/gfs2/meta_io.c, line = 492 and with UBSAN configured we also get complaints like [ 76.373395] UBSAN: shift-out-of-bounds in fs/gfs2/ops_fstype.c:295:19 [ 76.373815] shift exponent 4294967287 is too large for 64-bit type 'long unsigned int' After the patch, these complaints don't appear, mount fails immediately and we get an explanation in dmesg. Reported-by: syzbot+dcf33a7aae997956fe06@syzkaller.appspotmail.com Signed-off-by: Andrew Price <anprice@redhat.com> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Liu Kai <liukai284@huawei.com> --- fs/gfs2/ops_fstype.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c index ceecb4d82aef..bf7de0e8a1b0 100644 --- a/fs/gfs2/ops_fstype.c +++ b/fs/gfs2/ops_fstype.c @@ -172,7 +172,10 @@ static int gfs2_check_sb(struct gfs2_sbd *sdp, int silent) pr_warn("Invalid superblock size\n"); return -EINVAL; } - + if (sb->sb_bsize_shift != ffs(sb->sb_bsize) - 1) { + pr_warn("Invalid block size shift\n"); + return -EINVAL; + } return 0; } -- 2.34.1