On Tue, Apr 11, 2023 at 04:31:59PM -0700, 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(+) > > diff --git a/fs/xfs/xfs_buf_item_recover.c b/fs/xfs/xfs_buf_item_recover.c > index 5368a0d34452..ebe7f2c3cf63 100644 > --- a/fs/xfs/xfs_buf_item_recover.c > +++ b/fs/xfs/xfs_buf_item_recover.c > @@ -971,6 +971,16 @@ xlog_recover_buf_commit_pass2( > if (lsn && lsn != -1 && XFS_LSN_CMP(lsn, current_lsn) >= 0) { > trace_xfs_log_recover_buf_skip(log, buf_f); > xlog_recover_validate_buf_type(mp, bp, buf_f, NULLCOMMITLSN); > + > + /* > + * We're skipping replay of this buffer log item due to the log > + * item LSN being behind the ondisk buffer. Verify the buffer > + * contents since we aren't going to run the write verifier. > + */ > + if (bp->b_ops) { > + bp->b_ops->verify_read(bp); > + error = bp->b_error; > + } > goto out_release; > } Good catch - an unverified buffer in memory is definitely a landmine recovery shouldn't be leaving behind... Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> -- Dave Chinner david@xxxxxxxxxxxxx
