Syzbot has reported the following splat triggered by UBSAN: UBSAN: shift-out-of-bounds in fs/ocfs2/super.c:2336:10 shift exponent 32768 is too large for 32-bit type 'int' CPU: 2 UID: 0 PID: 5255 Comm: repro Not tainted 6.12.0-rc4-syzkaller-00047-gc2ee9f594da8 #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x241/0x360 ? __pfx_dump_stack_lvl+0x10/0x10 ? __pfx__printk+0x10/0x10 ? __asan_memset+0x23/0x50 ? lockdep_init_map_type+0xa1/0x910 __ubsan_handle_shift_out_of_bounds+0x3c8/0x420 ocfs2_fill_super+0xf9c/0x5750 ? __pfx_ocfs2_fill_super+0x10/0x10 ? __pfx_validate_chain+0x10/0x10 ? __pfx_validate_chain+0x10/0x10 ? validate_chain+0x11e/0x5920 ? __lock_acquire+0x1384/0x2050 ? __pfx_validate_chain+0x10/0x10 ? string+0x26a/0x2b0 ? widen_string+0x3a/0x310 ? string+0x26a/0x2b0 ? bdev_name+0x2b1/0x3c0 ? pointer+0x703/0x1210 ? __pfx_pointer+0x10/0x10 ? __pfx_format_decode+0x10/0x10 ? __lock_acquire+0x1384/0x2050 ? vsnprintf+0x1ccd/0x1da0 ? snprintf+0xda/0x120 ? __pfx_lock_release+0x10/0x10 ? do_raw_spin_lock+0x14f/0x370 ? __pfx_snprintf+0x10/0x10 ? set_blocksize+0x1f9/0x360 ? sb_set_blocksize+0x98/0xf0 ? setup_bdev_super+0x4e6/0x5d0 mount_bdev+0x20c/0x2d0 ? __pfx_ocfs2_fill_super+0x10/0x10 ? __pfx_mount_bdev+0x10/0x10 ? vfs_parse_fs_string+0x190/0x230 ? __pfx_vfs_parse_fs_string+0x10/0x10 legacy_get_tree+0xf0/0x190 ? __pfx_ocfs2_mount+0x10/0x10 vfs_get_tree+0x92/0x2b0 do_new_mount+0x2be/0xb40 ? __pfx_do_new_mount+0x10/0x10 __se_sys_mount+0x2d6/0x3c0 ? __pfx___se_sys_mount+0x10/0x10 ? do_syscall_64+0x100/0x230 ? __x64_sys_mount+0x20/0xc0 do_syscall_64+0xf3/0x230 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f37cae96fda Code: 48 8b 0d 51 ce 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 1e ce 0c 00 f7 d8 64 89 01 48 RSP: 002b:00007fff6c1aa228 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 00007fff6c1aa240 RCX: 00007f37cae96fda RDX: 00000000200002c0 RSI: 0000000020000040 RDI: 00007fff6c1aa240 RBP: 0000000000000004 R08: 00007fff6c1aa280 R09: 0000000000000000 R10: 00000000000008c0 R11: 0000000000000206 R12: 00000000000008c0 R13: 00007fff6c1aa280 R14: 0000000000000003 R15: 0000000001000000 </TASK> For a really damaged superblock, the value of 'i_super.s_blocksize_bits' may exceed the maximum possible shift for an underlying 'int'. So add an extra check whether the aforementioned field represents the valid block size, which is 512 bytes, 1K, 2K, or 4K. Reported-by: syzbot+56f7cd1abe4b8e475180@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=56f7cd1abe4b8e475180 Fixes: ccd979bdbce9 ("[PATCH] OCFS2: The Second Oracle Cluster Filesystem") Signed-off-by: Dmitry Antipov <dmantipov@xxxxxxxxx> --- v2: variable name and message nits as suggested by Joseph --- fs/ocfs2/super.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c index 3d404624bb96..c79b4291777f 100644 --- a/fs/ocfs2/super.c +++ b/fs/ocfs2/super.c @@ -2319,6 +2319,7 @@ static int ocfs2_verify_volume(struct ocfs2_dinode *di, struct ocfs2_blockcheck_stats *stats) { int status = -EAGAIN; + u32 blksz_bits; if (memcmp(di->i_signature, OCFS2_SUPER_BLOCK_SIGNATURE, strlen(OCFS2_SUPER_BLOCK_SIGNATURE)) == 0) { @@ -2333,11 +2334,15 @@ static int ocfs2_verify_volume(struct ocfs2_dinode *di, goto out; } status = -EINVAL; - if ((1 << le32_to_cpu(di->id2.i_super.s_blocksize_bits)) != blksz) { + /* Acceptable block sizes are 512 bytes, 1K, 2K and 4K. */ + blksz_bits = le32_to_cpu(di->id2.i_super.s_blocksize_bits); + if (blksz_bits < 9 || blksz_bits > 12) { mlog(ML_ERROR, "found superblock with incorrect block " - "size: found %u, should be %u\n", - 1 << le32_to_cpu(di->id2.i_super.s_blocksize_bits), - blksz); + "size bits: found %u, should be 9, 10, 11, or 12\n", + blksz_bits); + } else if ((1 << le32_to_cpu(blksz_bits)) != blksz) { + mlog(ML_ERROR, "found superblock with incorrect block " + "size: found %u, should be %u\n", 1 << blksz_bits, blksz); } else if (le16_to_cpu(di->id2.i_super.s_major_rev_level) != OCFS2_MAJOR_REV_LEVEL || le16_to_cpu(di->id2.i_super.s_minor_rev_level) != -- 2.47.0
