[syzbot] general protection fault in nilfs_palloc_commit_free_entry

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 440b7895c990 Merge tag 'mm-hotfixes-stable-2022-10-20' of ..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=17d3b33c880000
kernel config: https://syzkaller.appspot.com/x/.config?x=afc317c0f52ce670
dashboard link: https://syzkaller.appspot.com/bug?extid=ebe05ee8e98f755f61d0
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d81572880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=162b0a36880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/105038975fc9/disk-440b7895.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/edd7302c8fc8/vmlinux-440b7895.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/6a01cad872ec/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ebe05e...@syzkaller.appspotmail.com

NILFS (loop0): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 1 PID: 3613 Comm: segctord Not tainted 6.1.0-rc1-syzkaller-00158-g440b7895c990 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
RIP: 0010:nilfs_palloc_commit_free_entry+0xd2/0x570 fs/nilfs2/alloc.c:608
Code: 08 4c 89 f8 48 c1 e8 03 48 89 44 24 18 42 80 3c 20 00 74 08 4c 89 ff e8 4c 36 8b fe 49 8b 2f 48 83 c5 10 48 89 e8 48 c1 e8 03 <42> 80 3c 20 00 74 08 48 89 ef e8 2f 36 8b fe 48 8b 45 00 48 89 44
RSP: 0018:ffffc90003d8f280 EFLAGS: 00010202
RAX: 0000000000000002 RBX: 1ffff1100e5b4044 RCX: 0000000000002000
RDX: 0000000000001801 RSI: 000000000000000a RDI: 000000000000003d
RBP: 0000000000000010 R08: ffffffff835085a5 R09: ffffed100e093a2a
R10: ffffed100e093a2a R11: 1ffff1100e093a29 R12: dffffc0000000000
R13: 0000000000002000 R14: ffff888072da0222 R15: ffff88802435cba0
FS: 0000000000000000(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa887c6b1d0 CR3: 000000000c88e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
nilfs_dat_commit_update+0x25/0x40 fs/nilfs2/dat.c:236
nilfs_btree_commit_update_v+0x91/0x420 fs/nilfs2/btree.c:1940
nilfs_btree_commit_propagate_v fs/nilfs2/btree.c:2016 [inline]
nilfs_btree_propagate_v fs/nilfs2/btree.c:2046 [inline]
nilfs_btree_propagate+0x972/0xe10 fs/nilfs2/btree.c:2088
nilfs_bmap_propagate+0x6d/0x120 fs/nilfs2/bmap.c:337
nilfs_collect_file_data+0x49/0xc0 fs/nilfs2/segment.c:568
nilfs_segctor_apply_buffers+0x192/0x380 fs/nilfs2/segment.c:1018
nilfs_segctor_scan_file+0x842/0xaf0 fs/nilfs2/segment.c:1067
nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1197 [inline]
nilfs_segctor_collect fs/nilfs2/segment.c:1503 [inline]
nilfs_segctor_do_construct+0x1d2c/0x6f80 fs/nilfs2/segment.c:2045
nilfs_segctor_construct+0x143/0x8d0 fs/nilfs2/segment.c:2379
nilfs_segctor_thread_construct fs/nilfs2/segment.c:2487 [inline]
nilfs_segctor_thread+0x59e/0x11c0 fs/nilfs2/segment.c:2570
kthread+0x266/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:nilfs_palloc_commit_free_entry+0xd2/0x570 fs/nilfs2/alloc.c:608
Code: 08 4c 89 f8 48 c1 e8 03 48 89 44 24 18 42 80 3c 20 00 74 08 4c 89 ff e8 4c 36 8b fe 49 8b 2f 48 83 c5 10 48 89 e8 48 c1 e8 03 <42> 80 3c 20 00 74 08 48 89 ef e8 2f 36 8b fe 48 8b 45 00 48 89 44
RSP: 0018:ffffc90003d8f280 EFLAGS: 00010202
RAX: 0000000000000002 RBX: 1ffff1100e5b4044 RCX: 0000000000002000
RDX: 0000000000001801 RSI: 000000000000000a RDI: 000000000000003d
RBP: 0000000000000010 R08: ffffffff835085a5 R09: ffffed100e093a2a
R10: ffffed100e093a2a R11: 1ffff1100e093a29 R12: dffffc0000000000
R13: 0000000000002000 R14: ffff888072da0222 R15: ffff88802435cba0
FS: 0000000000000000(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa887c6b1d0 CR3: 000000000c88e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 08 4c 89 f8 or %cl,-0x8(%rcx,%rcx,4)
4: 48 c1 e8 03 shr $0x3,%rax
8: 48 89 44 24 18 mov %rax,0x18(%rsp)
d: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1)
12: 74 08 je 0x1c
14: 4c 89 ff mov %r15,%rdi
17: e8 4c 36 8b fe callq 0xfe8b3668
1c: 49 8b 2f mov (%r15),%rbp
1f: 48 83 c5 10 add $0x10,%rbp
23: 48 89 e8 mov %rbp,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 48 89 ef mov %rbp,%rdi
34: e8 2f 36 8b fe callq 0xfe8b3668
39: 48 8b 45 00 mov 0x0(%rbp),%rax
3d: 48 rex.W
3e: 89 .byte 0x89
3f: 44 rex.R


---
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[Ryusuke Konishi]

From: ZhangPeng <zhangp...@huawei.com>

Syzbot reported a null-ptr-deref bug:

NILFS (loop0): segctord starting. Construction interval = 5 seconds, CP
frequency < 30 seconds
general protection fault, probably for non-canonical address
0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]

CPU: 1 PID: 3603 Comm: segctord Not tainted
6.1.0-rc2-syzkaller-00105-gb229b6ca5abb #0
Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google
10/11/2022
RIP: 0010:nilfs_palloc_commit_free_entry+0xe5/0x6b0
fs/nilfs2/alloc.c:608
Code: 00 00 00 00 fc ff df 80 3c 02 00 0f 85 cd 05 00 00 48 b8 00 00 00
00 00 fc ff df 4c 8b 73 08 49 8d 7e 10 48 89 fa 48 c1 ea 03 <80> 3c 02
00 0f 85 26 05 00 00 49 8b 46 10 be a6 00 00 00 48 c7 c7
RSP: 0018:ffffc90003dff830 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: ffff88802594e218 RCX: 000000000000000d
RDX: 0000000000000002 RSI: 0000000000002000 RDI: 0000000000000010
RBP: ffff888071880222 R08: 0000000000000005 R09: 000000000000003f
R10: 000000000000000d R11: 0000000000000000 R12: ffff888071880158
R13: ffff88802594e220 R14: 0000000000000000 R15: 0000000000000004

FS: 0000000000000000(0000) GS:ffff8880b9b00000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007fb1c08316a8 CR3: 0000000018560000 CR4: 0000000000350ee0
Call Trace:
<TASK>
nilfs_dat_commit_free fs/nilfs2/dat.c:114 [inline]
nilfs_dat_commit_end+0x464/0x5f0 fs/nilfs2/dat.c:193
nilfs_dat_commit_update+0x26/0x40 fs/nilfs2/dat.c:236
nilfs_btree_commit_update_v+0x87/0x4a0 fs/nilfs2/btree.c:1940

nilfs_btree_commit_propagate_v fs/nilfs2/btree.c:2016 [inline]
nilfs_btree_propagate_v fs/nilfs2/btree.c:2046 [inline]

nilfs_btree_propagate+0xa00/0xd60 fs/nilfs2/btree.c:2088
nilfs_bmap_propagate+0x73/0x170 fs/nilfs2/bmap.c:337
nilfs_collect_file_data+0x45/0xd0 fs/nilfs2/segment.c:568
nilfs_segctor_apply_buffers+0x14a/0x470 fs/nilfs2/segment.c:1018
nilfs_segctor_scan_file+0x3f4/0x6f0 fs/nilfs2/segment.c:1067

nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1197 [inline]
nilfs_segctor_collect fs/nilfs2/segment.c:1503 [inline]

nilfs_segctor_do_construct+0x12fc/0x6af0 fs/nilfs2/segment.c:2045
nilfs_segctor_construct+0x8e3/0xb30 fs/nilfs2/segment.c:2379
nilfs_segctor_thread_construct fs/nilfs2/segment.c:2487 [inline]
nilfs_segctor_thread+0x3c3/0xf30 fs/nilfs2/segment.c:2570
kthread+0x2e4/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>
...

If DAT metadata file is corrupted on disk, there is a case where
req->pr_desc_bh is NULL and blocknr is 0 at nilfs_dat_commit_end()
during a b-tree operation that cascadingly updates ancestor nodes of
the b-tree, because nilfs_dat_commit_alloc() for a lower level block can
initialize the blocknr on the same DAT entry between
nilfs_dat_prepare_end() and nilfs_dat_commit_end().

If this happens, nilfs_dat_commit_end() calls nilfs_dat_commit_free()
without valid buffer heads in req->pr_desc_bh and req->pr_bitmap_bh, and
causes the NULL pointer dereference above in
nilfs_palloc_commit_free_entry() function, which leads to a crash.

Fix this by adding a NULL check on req->pr_desc_bh and req->pr_bitmap_bh
before nilfs_palloc_commit_free_entry() in nilfs_dat_commit_free().

This also calls nilfs_error() in that case to notify that there is a
fatal flaw in the filesystem metadata and prevent further operations.

Link: https://lkml.kernel.org/r/00000000000097...@google.com
Link: https://lkml.kernel.org/r/20221114040441.164...@huawei.com
Signed-off-by: ZhangPeng <zhangp...@huawei.com>
Reported-by: syzbot+ebe05e...@syzkaller.appspotmail.com
Signed-off-by: Ryusuke Konishi <konishi...@gmail.com>
Tested-by: Ryusuke Konishi <konishi...@gmail.com>
Cc: sta...@vger.kernel.org
---
Please apply this bugfix to -mm tree.

This is the first time I send this to you, but I prefixed this as a v2 patch
since this has the following changes from the original LKML post by ZhangPeng
base on the discussion and consent with him.
v1 -> v2:
1) Use "unlikely" annotation since this usually doesn't happen.
2) Call nilfs_error to notify the fatal flaw in the filesystem metadata and
prevent further operations.
3) Modify changelog description base on detailed analysis.
4) Add tags ("Tested-by", cc-stable, and links).

fs/nilfs2/dat.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/fs/nilfs2/dat.c b/fs/nilfs2/dat.c
index 3b55e239705f..9930fa901039 100644
--- a/fs/nilfs2/dat.c
+++ b/fs/nilfs2/dat.c
@@ -111,6 +111,13 @@ static void nilfs_dat_commit_free(struct inode *dat,
kunmap_atomic(kaddr);

nilfs_dat_commit_entry(dat, req);
+
+ if (unlikely(req->pr_desc_bh == NULL || req->pr_bitmap_bh == NULL)) {
+ nilfs_error(dat->i_sb,
+ "state inconsistency probably due to duplicate use of vblocknr = %llu",
+ (unsigned long long)req->pr_entry_nr);
+ return;
+ }
nilfs_palloc_commit_free_entry(dat, req);
}

--
2.34.1