general protection fault in nilfs_palloc_commit_free_entry

syzbot Applied syzbot 2 participants 2 messages Oct 23, 2022 – Nov 19, 2022 NILFS2 filesystem

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author syzbot

2022-10-23 07:29 UTC #0 lore raw

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+ebe05ee8e98f755f61d0-Pl5Pbv+GP7P466ipTTIvnc23WoclnBCfAL8bYrjMMd8@public.gmane.org

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

maintainer

2022-11-19 12:05 UTC #1 lore raw

PATCH v2 1/1 nilfs2: fix NULL pointer dereference in nilfs_palloc_commit_free_entry()

From: ZhangPeng <[email protected]>

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/00000000000097c20205ebaea3d6-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org open here

Link https://lkml.kernel.org/r/20221114040441.1649940-1-zhangpeng362-hv44wF8Li93QT0dZR+AlfA@public.gmane.org open here

Signed-off-by ZhangPeng <[email protected]>

Reported-by syzbot+ebe05ee8e98f755f61d0-Pl5Pbv+GP7P466ipTTIvnc23WoclnBCfAL8bYrjMMd8@public.gmane.org

Signed-off-by Ryusuke Konishi <[email protected]>

Tested-by Ryusuke Konishi <[email protected]>

Cc [email protected]

---
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(+)

fs/nilfs2/dat.c +7 -0

index 3b55e239705f..9930fa901039 100644
@@ -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);
 }

Signature · 1 line

2.34.1