On Thu, Jun 1, 2023 at 6:18 PM Darrick J. Wong <djwong@xxxxxxxxxx> wrote: > > On Thu, Jun 01, 2023 at 02:03:51PM +0100, Lee Jones wrote: > > Hi Darrick, > > > > On Tue, 11 Apr 2023, Darrick J. Wong wrote: > > > > > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > > > > > syzbot detected a crash during log recovery: > > > > > > XFS (loop0): Mounting V5 Filesystem bfdc47fc-10d8-4eed-a562-11a831b3f791 > > > XFS (loop0): Torn write (CRC failure) detected at log block 0x180. Truncating head block from 0x200. > > > XFS (loop0): Starting recovery (logdev: internal) > > > ================================================================== > > > BUG: KASAN: slab-out-of-bounds in xfs_btree_lookup_get_block+0x15c/0x6d0 fs/xfs/libxfs/xfs_btree.c:1813 > > > Read of size 8 at addr ffff88807e89f258 by task syz-executor132/5074 > > > > > > CPU: 0 PID: 5074 Comm: syz-executor132 Not tainted 6.2.0-rc1-syzkaller #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 > > > Call Trace: > > > <TASK> > > > __dump_stack lib/dump_stack.c:88 [inline] > > > dump_stack_lvl+0x1b1/0x290 lib/dump_stack.c:106 > > > print_address_description+0x74/0x340 mm/kasan/report.c:306 > > > print_report+0x107/0x1f0 mm/kasan/report.c:417 > > > kasan_report+0xcd/0x100 mm/kasan/report.c:517 > > > xfs_btree_lookup_get_block+0x15c/0x6d0 fs/xfs/libxfs/xfs_btree.c:1813 > > > xfs_btree_lookup+0x346/0x12c0 fs/xfs/libxfs/xfs_btree.c:1913 > > > xfs_btree_simple_query_range+0xde/0x6a0 fs/xfs/libxfs/xfs_btree.c:4713 > > > xfs_btree_query_range+0x2db/0x380 fs/xfs/libxfs/xfs_btree.c:4953 > > > xfs_refcount_recover_cow_leftovers+0x2d1/0xa60 fs/xfs/libxfs/xfs_refcount.c:1946 > > > xfs_reflink_recover_cow+0xab/0x1b0 fs/xfs/xfs_reflink.c:930 > > > xlog_recover_finish+0x824/0x920 fs/xfs/xfs_log_recover.c:3493 > > > xfs_log_mount_finish+0x1ec/0x3d0 fs/xfs/xfs_log.c:829 > > > xfs_mountfs+0x146a/0x1ef0 fs/xfs/xfs_mount.c:933 > > > xfs_fs_fill_super+0xf95/0x11f0 fs/xfs/xfs_super.c:1666 > > > get_tree_bdev+0x400/0x620 fs/super.c:1282 > > > vfs_get_tree+0x88/0x270 fs/super.c:1489 > > > do_new_mount+0x289/0xad0 fs/namespace.c:3145 > > > do_mount fs/namespace.c:3488 [inline] > > > __do_sys_mount fs/namespace.c:3697 [inline] > > > __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674 > > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > > do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 > > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > > RIP: 0033:0x7f89fa3f4aca > > > Code: 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 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 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 > > > RSP: 002b:00007fffd5fb5ef8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5 > > > RAX: ffffffffffffffda RBX: 00646975756f6e2c RCX: 00007f89fa3f4aca > > > RDX: 0000000020000100 RSI: 0000000020009640 RDI: 00007fffd5fb5f10 > > > RBP: 00007fffd5fb5f10 R08: 00007fffd5fb5f50 R09: 000000000000970d > > > R10: 0000000000200800 R11: 0000000000000206 R12: 0000000000000004 > > > R13: 0000555556c6b2c0 R14: 0000000000200800 R15: 00007fffd5fb5f50 > > > </TASK> > > > > > > The fuzzed image contains an AGF with an obviously garbage > > > agf_refcount_level value of 32, and a dirty log with a buffer log item > > > for that AGF. The ondisk AGF has a higher LSN than the recovered log > > > item. xlog_recover_buf_commit_pass2 reads the buffer, compares the > > > LSNs, and decides to skip replay because the ondisk buffer appears to be > > > newer. > > > > > > Unfortunately, the ondisk buffer is corrupt, but recovery just read the > > > buffer with no buffer ops specified: > > > > > > error = xfs_buf_read(mp->m_ddev_targp, buf_f->blf_blkno, > > > buf_f->blf_len, buf_flags, &bp, NULL); > > > > > > Skipping the buffer leaves its contents in memory unverified. This sets > > > us up for a kernel crash because xfs_refcount_recover_cow_leftovers > > > reads the buffer (which is still around in XBF_DONE state, so no read > > > verification) and creates a refcountbt cursor of height 32. This is > > > impossible so we run off the end of the cursor object and crash. > > > > > > Fix this by invoking the verifier on all skipped buffers and aborting > > > log recovery if the ondisk buffer is corrupt. It might be smarter to > > > force replay the log item atop the buffer and then see if it'll pass the > > > write verifier (like ext4 does) but for now let's go with the > > > conservative option where we stop immediately. > > > > > > Link: https://syzkaller.appspot.com/bug?extid=7e9494b8b399902e994e > > > Fixes: 67dc288c2106 ("xfs: ensure verifiers are attached to recovered buffers") > > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> > > > --- > > > fs/xfs/xfs_buf_item_recover.c | 10 ++++++++++ > > > 1 file changed, 10 insertions(+) > > > > Rightly or wrongly, CVE-2023-212 has been raised against this issue. > > > > It looks as though the Fixes: tag above was stripped when applied. > > > > Should this still be submitted to Stable? > > Yes, but we have not been successful in persuading any company to pick > up stable backporting and QA for any kernel newer than 5.15. > I already have a kdevops baseline that I established for xfs-6.1.y when I backported the SGID vfs fixes, so it is not a problem for me to test this patch (or any other if you have hints). I have not yet invested in selecting patches for backport, partly because Leah wrote that she intends to take this up. Leah, if your priorities have changed, I can try to start collecting candidates for backport in my spare time, whenever that will be. In any case, testing the occasional patch for 6.1.y is something that I can do until a company/distro becomes the owner of xfs-6.1.y. Darrick et al., If you want me to test any other patches for 6.1.y, please let me know. Thanks, Amir.
