120 lines
5.7 KiB
Diff
120 lines
5.7 KiB
Diff
From 124abc5a2d892bffaa2830d3d596f087555f0fd3 Mon Sep 17 00:00:00 2001
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From: "Darrick J. Wong" <djwong@kernel.org>
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Date: Tue, 8 Aug 2023 12:41:24 +0000
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Subject: [PATCH 5/7] xfs: verify buffer contents when we skip log replay
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commit 22ed903eee23a5b174e240f1cdfa9acf393a5210 upstream
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Author: Darrick J. Wong <djwong@kernel.org>
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Date: Wed Apr 12 15:49:23 2023 +1000
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xfs: verify buffer contents when we skip log replay
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syzbot detected a crash during log recovery:
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XFS (loop0): Mounting V5 Filesystem bfdc47fc-10d8-4eed-a562-11a831b3f791
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XFS (loop0): Torn write (CRC failure) detected at log block 0x180. Truncating head block from 0x200.
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XFS (loop0): Starting recovery (logdev: internal)
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==================================================================
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BUG: KASAN: slab-out-of-bounds in xfs_btree_lookup_get_block+0x15c/0x6d0 fs/xfs/libxfs/xfs_btree.c:1813
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Read of size 8 at addr ffff88807e89f258 by task syz-executor132/5074
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CPU: 0 PID: 5074 Comm: syz-executor132 Not tainted 6.2.0-rc1-syzkaller #0
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Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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Call Trace:
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<TASK>
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__dump_stack lib/dump_stack.c:88 [inline]
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dump_stack_lvl+0x1b1/0x290 lib/dump_stack.c:106
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print_address_description+0x74/0x340 mm/kasan/report.c:306
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print_report+0x107/0x1f0 mm/kasan/report.c:417
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kasan_report+0xcd/0x100 mm/kasan/report.c:517
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xfs_btree_lookup_get_block+0x15c/0x6d0 fs/xfs/libxfs/xfs_btree.c:1813
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xfs_btree_lookup+0x346/0x12c0 fs/xfs/libxfs/xfs_btree.c:1913
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xfs_btree_simple_query_range+0xde/0x6a0 fs/xfs/libxfs/xfs_btree.c:4713
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xfs_btree_query_range+0x2db/0x380 fs/xfs/libxfs/xfs_btree.c:4953
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xfs_refcount_recover_cow_leftovers+0x2d1/0xa60 fs/xfs/libxfs/xfs_refcount.c:1946
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xfs_reflink_recover_cow+0xab/0x1b0 fs/xfs/xfs_reflink.c:930
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xlog_recover_finish+0x824/0x920 fs/xfs/xfs_log_recover.c:3493
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xfs_log_mount_finish+0x1ec/0x3d0 fs/xfs/xfs_log.c:829
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xfs_mountfs+0x146a/0x1ef0 fs/xfs/xfs_mount.c:933
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xfs_fs_fill_super+0xf95/0x11f0 fs/xfs/xfs_super.c:1666
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get_tree_bdev+0x400/0x620 fs/super.c:1282
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vfs_get_tree+0x88/0x270 fs/super.c:1489
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do_new_mount+0x289/0xad0 fs/namespace.c:3145
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do_mount fs/namespace.c:3488 [inline]
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__do_sys_mount fs/namespace.c:3697 [inline]
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__se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674
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do_syscall_x64 arch/x86/entry/common.c:50 [inline]
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do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
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entry_SYSCALL_64_after_hwframe+0x63/0xcd
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RIP: 0033:0x7f89fa3f4aca
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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
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RSP: 002b:00007fffd5fb5ef8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
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RAX: ffffffffffffffda RBX: 00646975756f6e2c RCX: 00007f89fa3f4aca
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RDX: 0000000020000100 RSI: 0000000020009640 RDI: 00007fffd5fb5f10
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RBP: 00007fffd5fb5f10 R08: 00007fffd5fb5f50 R09: 000000000000970d
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R10: 0000000000200800 R11: 0000000000000206 R12: 0000000000000004
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R13: 0000555556c6b2c0 R14: 0000000000200800 R15: 00007fffd5fb5f50
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</TASK>
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The fuzzed image contains an AGF with an obviously garbage
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agf_refcount_level value of 32, and a dirty log with a buffer log item
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for that AGF. The ondisk AGF has a higher LSN than the recovered log
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item. xlog_recover_buf_commit_pass2 reads the buffer, compares the
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LSNs, and decides to skip replay because the ondisk buffer appears to be
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newer.
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Unfortunately, the ondisk buffer is corrupt, but recovery just read the
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buffer with no buffer ops specified:
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error = xfs_buf_read(mp->m_ddev_targp, buf_f->blf_blkno,
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buf_f->blf_len, buf_flags, &bp, NULL);
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Skipping the buffer leaves its contents in memory unverified. This sets
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us up for a kernel crash because xfs_refcount_recover_cow_leftovers
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reads the buffer (which is still around in XBF_DONE state, so no read
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verification) and creates a refcountbt cursor of height 32. This is
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impossible so we run off the end of the cursor object and crash.
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Fix this by invoking the verifier on all skipped buffers and aborting
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log recovery if the ondisk buffer is corrupt. It might be smarter to
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force replay the log item atop the buffer and then see if it'll pass the
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write verifier (like ext4 does) but for now let's go with the
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conservative option where we stop immediately.
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Link: https://syzkaller.appspot.com/bug?extid=7e9494b8b399902e994e
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Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Reviewed-by: Dave Chinner <dchinner@redhat.com>
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Signed-off-by: Dave Chinner <david@fromorbit.com>
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CVE: CVE-2023-2124
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Signed-off-by: Nagappan Ramasamy Palaniappan <nagappan.ramasamy.palaniappan@oracle.com>
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Reviewed-by: Laurence Rochfort <laurence.rochfort@oracle.com>
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---
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fs/xfs/xfs_buf_item_recover.c | 10 ++++++++++
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1 file changed, 10 insertions(+)
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diff --git a/fs/xfs/xfs_buf_item_recover.c b/fs/xfs/xfs_buf_item_recover.c
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index aa4d45701..e8eeaf005 100644
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--- a/fs/xfs/xfs_buf_item_recover.c
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+++ b/fs/xfs/xfs_buf_item_recover.c
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@@ -934,6 +934,16 @@ xlog_recover_buf_commit_pass2(
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if (lsn && lsn != -1 && XFS_LSN_CMP(lsn, current_lsn) >= 0) {
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trace_xfs_log_recover_buf_skip(log, buf_f);
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xlog_recover_validate_buf_type(mp, bp, buf_f, NULLCOMMITLSN);
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+
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+ /*
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+ * We're skipping replay of this buffer log item due to the log
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+ * item LSN being behind the ondisk buffer. Verify the buffer
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+ * contents since we aren't going to run the write verifier.
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+ */
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+ if (bp->b_ops) {
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+ bp->b_ops->verify_read(bp);
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+ error = bp->b_error;
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+ }
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goto out_release;
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}
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--
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2.31.1
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