[syzbot] [fs?] KASAN: null-ptr-deref Write in get_block (2)

syzbot
2023-05-22T22:36:18Z

Hello,

syzbot found the following issue on:

HEAD commit: 4d6d4c7f541d Merge tag 'linux-kselftest-fixes-6.4-rc3' of ..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=17b34a5a280000
kernel config: https://syzkaller.appspot.com/x/.config?x=94af80bb8ddd23c4
dashboard link: https://syzkaller.appspot.com/bug?extid=aad58150cbc64ba41bdc
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1615fbe9280000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1282842e280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dcd8898335fc/disk-4d6d4c7f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6a1f7abe57aa/vmlinux-4d6d4c7f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b485f41c18e6/bzImage-4d6d4c7f.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/19be7546cd7d/mount_1.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+aad58150cbc64ba41bdc@syzkaller.appspotmail.com

memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=4996 'syz-executor412'
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:96 [inline]
BUG: KASAN: null-ptr-deref in test_and_set_bit_lock include/asm-generic/bitops/instrumented-lock.h:57 [inline]
BUG: KASAN: null-ptr-deref in trylock_buffer include/linux/buffer_head.h:399 [inline]
BUG: KASAN: null-ptr-deref in lock_buffer include/linux/buffer_head.h:405 [inline]
BUG: KASAN: null-ptr-deref in alloc_branch fs/sysv/itree.c:148 [inline]
BUG: KASAN: null-ptr-deref in get_block+0x567/0x16a0 fs/sysv/itree.c:251
Write of size 8 at addr 0000000000000000 by task syz-executor412/4996

CPU: 1 PID: 4996 Comm: syz-executor412 Not tainted 6.4.0-rc2-syzkaller-00018-g4d6d4c7f541d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
print_report+0xe6/0x540 mm/kasan/report.c:465
kasan_report+0x176/0x1b0 mm/kasan/report.c:572
kasan_check_range+0x283/0x290 mm/kasan/generic.c:187
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
test_and_set_bit_lock include/asm-generic/bitops/instrumented-lock.h:57 [inline]
trylock_buffer include/linux/buffer_head.h:399 [inline]
lock_buffer include/linux/buffer_head.h:405 [inline]
alloc_branch fs/sysv/itree.c:148 [inline]
get_block+0x567/0x16a0 fs/sysv/itree.c:251
__block_write_begin_int+0x548/0x1a50 fs/buffer.c:2064
__block_write_begin fs/buffer.c:2114 [inline]
block_write_begin+0x9c/0x1f0 fs/buffer.c:2175
sysv_write_begin+0x31/0x70 fs/sysv/itree.c:485
generic_perform_write+0x300/0x5e0 mm/filemap.c:3923
__generic_file_write_iter+0x17a/0x400 mm/filemap.c:4051
generic_file_write_iter+0xaf/0x310 mm/filemap.c:4083
do_iter_write+0x7b1/0xcb0 fs/read_write.c:860
vfs_writev fs/read_write.c:933 [inline]
do_pwritev+0x21a/0x360 fs/read_write.c:1030
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f3233222b19
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:00007ffecf15f268 EFLAGS: 00000246 ORIG_RAX: 0000000000000128
RAX: ffffffffffffffda RBX: 0031656c69662f2e RCX: 00007f3233222b19
RDX: 0000000000000005 RSI: 0000000020000480 RDI: 0000000000000004
RBP: 00007f32331e2150 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000007fff R11: 0000000000000246 R12: 00007f32331e21e0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
==================================================================

---
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