CVE-2022-49769

01/Description

In the Linux kernel, the following vulnerability has been resolved: gfs2: Check sb_bsize_shift after reading superblock 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.

02/Affected products

linux: linux kernel

03/References8

• git.kernel.org/stable/c/15c83fa0fd659dd9fbdc940a560b61236e876a80 Patch
• git.kernel.org/stable/c/16670534c7cff1acd918a6a5ec751b14e7436b76 Patch
• git.kernel.org/stable/c/1ad197097343568066a8ffaa27ee7d0ae6d9f476 Patch
• git.kernel.org/stable/c/28275a7c84d21c55ab3282d897f284d8d527173c Patch
• git.kernel.org/stable/c/5fa30be7ba81191b0a0c7239a89befc0c94286d5 Patch
• git.kernel.org/stable/c/670f8ce56dd0632dc29a0322e188cc73ce3c6b92 Patch
• git.kernel.org/stable/c/8b6534c9ae9dba5489703a19d8ba6c8f2cfa33c2 Patch
• git.kernel.org/stable/c/d6b1e8ea6f3418c3b461ad5a35cdc93c996b2c87 Patch