KASAN: null-ptr-deref Write in get_block

Status: fixed on 2023/10/03 00:08
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+77fdbc31129a13c474ce@syzkaller.appspotmail.com
Fix commit: ea2b62f30589 fs/sysv: Null check to prevent null-ptr-deref bug
First crash: 1146d, last: 1100d
Fix bisection: fixed by (bisect log) :
commit afd9a31b5aa4b3747f382d44a7b03b7b5d0b7635
Author: Prince Kumar Maurya <princekumarmaurya06@gmail.com>
Date: Wed May 31 01:31:41 2023 +0000

  fs/sysv: Null check to prevent null-ptr-deref bug

  
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2023/08/01 linux-5.15.y (ToT) 09996673e313 C [report] KASAN: null-ptr-deref Write in get_block
2023/06/17 upstream (ToT) 1639fae5132b C [report] KASAN: null-ptr-deref Write in get_block
2023/08/01 upstream (ToT) 5d0c230f1de8 C Didn't crash
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: null-ptr-deref Write in get_block origin:upstream missing-backport 12 syz, C done 4 1098d 1143d 3/3 fixed on 2023/10/02 12:03
upstream KASAN: null-ptr-deref Write in get_block (2) fs 12 syz, C error 11 1137d 1171d 23/29 fixed on 2023/09/28 17:51
upstream KASAN: null-ptr-deref Write in get_block fs 12 syz, C done 101 2215d 2328d 15/29 fixed on 2020/09/16 22:51
linux-4.14 BUG: unable to handle kernel NULL pointer dereference in get_block (2) 10 syz, C 1 1253d 1335d 0/1 upstream: reported C repro on 2022/12/09 08:52
upstream KASAN: slab-out-of-bounds Read in get_block (2) fs 17 1 1305d 1305d 0/29 auto-obsoleted due to no activity on 2023/05/09 01:15

Sample crash report:
loop0: detected capacity change from 0 to 128
VFS: Found a Xenix FS (block size = 512) on device loop0
sysv_free_block: trying to free block not in datazone
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: null-ptr-deref in test_and_set_bit_lock include/asm-generic/bitops/instrumented-lock.h:55 [inline]
BUG: KASAN: null-ptr-deref in trylock_buffer include/linux/buffer_head.h:395 [inline]
BUG: KASAN: null-ptr-deref in lock_buffer include/linux/buffer_head.h:401 [inline]
BUG: KASAN: null-ptr-deref in alloc_branch fs/sysv/itree.c:148 [inline]
BUG: KASAN: null-ptr-deref in get_block+0x565/0x1690 fs/sysv/itree.c:251
Write of size 8 at addr 0000000000000000 by task syz-executor311/3498

CPU: 0 PID: 3498 Comm: syz-executor311 Not tainted 5.15.117-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 __kasan_report mm/kasan/report.c:438 [inline]
 kasan_report+0x161/0x1c0 mm/kasan/report.c:451
 kasan_check_range+0x27e/0x290 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 test_and_set_bit_lock include/asm-generic/bitops/instrumented-lock.h:55 [inline]
 trylock_buffer include/linux/buffer_head.h:395 [inline]
 lock_buffer include/linux/buffer_head.h:401 [inline]
 alloc_branch fs/sysv/itree.c:148 [inline]
 get_block+0x565/0x1690 fs/sysv/itree.c:251
 __block_write_begin_int+0x60b/0x1650 fs/buffer.c:2012
 __block_write_begin fs/buffer.c:2062 [inline]
 block_write_begin+0x4f/0xc0 fs/buffer.c:2122
 sysv_write_begin+0x36/0x70 fs/sysv/itree.c:485
 generic_perform_write+0x2bf/0x5b0 mm/filemap.c:3776
 __generic_file_write_iter+0x243/0x4f0 mm/filemap.c:3903
 generic_file_write_iter+0xa7/0x1b0 mm/filemap.c:3935
 do_iter_readv_writev+0x594/0x7a0
 do_iter_write+0x1ea/0x760 fs/read_write.c:855
 vfs_writev fs/read_write.c:928 [inline]
 do_pwritev+0x219/0x360 fs/read_write.c:1025
 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+0x61/0xcb
RIP: 0033:0x7fbb39e5db29
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 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:00007ffda20a7508 EFLAGS: 00000246 ORIG_RAX: 0000000000000128
RAX: ffffffffffffffda RBX: 0031656c69662f2e RCX: 00007fbb39e5db29
RDX: 0000000000000005 RSI: 0000000020000480 RDI: 0000000000000004
RBP: 00007fbb39e1d160 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000007fff R11: 0000000000000246 R12: 00007fbb39e1d1f0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/06/17 01:00 linux-5.15.y 471e639e59d1 f3921d4d .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan KASAN: null-ptr-deref Write in get_block
2023/06/29 05:45 linux-5.15.y 4af60700a60c ca69c785 .config console log report info ci2-linux-5-15-kasan KASAN: null-ptr-deref Write in get_block
* Struck through repros no longer work on HEAD.