Re: [syzbot] [ext4?] general protection fault in __block_commit_write

syzbot
2024-05-20T01:52:26Z

syzbot has found a reproducer for the following issue on:

HEAD commit: fda5695d692c Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=1624be58980000
kernel config: https://syzkaller.appspot.com/x/.config?x=95dc1de8407c7270
dashboard link: https://syzkaller.appspot.com/bug?extid=18df508cf00a0598d9a6
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12bef634980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10b68242980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/07f3214ff0d9/disk-fda5695d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/70e2e2c864e8/vmlinux-fda5695d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b259942a16dc/Image-fda5695d.gz.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/5853ffd99deb/mount_0.gz
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/8d78b07027fb/mount_5.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+18df508cf00a0598d9a6@syzkaller.appspotmail.com

Unable to handle kernel paging request at virtual address dfff800000000004
KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
Mem abort info:
ESR = 0x0000000096000005
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x05: level 1 translation fault
Data abort info:
ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
CM = 0, WnR = 0, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[dfff800000000004] address between user and kernel address ranges
Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 20274 Comm: syz-executor185 Not tainted 6.9.0-rc7-syzkaller-gfda5695d692c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __block_commit_write+0x64/0x2b0 fs/buffer.c:2167
lr : __block_commit_write+0x3c/0x2b0 fs/buffer.c:2160
sp : ffff8000a1957600
x29: ffff8000a1957610 x28: dfff800000000000 x27: ffff0000e30e34b0
x26: 0000000000000000 x25: dfff800000000000 x24: dfff800000000000
x23: fffffdffc397c9e0 x22: 0000000000000020 x21: 0000000000000020
x20: 0000000000000040 x19: fffffdffc397c9c0 x18: 1fffe000367bd196
x17: ffff80008eead000 x16: ffff80008ae89e3c x15: 00000000200000c0
x14: 1fffe0001cbe4e04 x13: 0000000000000000 x12: 0000000000000000
x11: 0000000000000001 x10: 0000000000ff0100 x9 : 0000000000000000
x8 : 0000000000000004 x7 : 0000000000000000 x6 : 0000000000000000
x5 : fffffdffc397c9c0 x4 : 0000000000000020 x3 : 0000000000000020
x2 : 0000000000000040 x1 : 0000000000000020 x0 : fffffdffc397c9c0
Call trace:
__block_commit_write+0x64/0x2b0 fs/buffer.c:2167
block_write_end+0xb4/0x104 fs/buffer.c:2253
ext4_da_do_write_end fs/ext4/inode.c:2955 [inline]
ext4_da_write_end+0x2c4/0xa40 fs/ext4/inode.c:3028
generic_perform_write+0x394/0x588 mm/filemap.c:3985
ext4_buffered_write_iter+0x2c0/0x4ec fs/ext4/file.c:299
ext4_file_write_iter+0x188/0x1780
call_write_iter include/linux/fs.h:2110 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0x968/0xc3c fs/read_write.c:590
ksys_write+0x15c/0x26c fs/read_write.c:643
__do_sys_write fs/read_write.c:655 [inline]
__se_sys_write fs/read_write.c:652 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:652
__invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152
el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
Code: 97f85911 f94002da 91008356 d343fec8 (38796908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 97f85911 bl 0xffffffffffe16444
4: f94002da ldr x26, [x22]
8: 91008356 add x22, x26, #0x20
c: d343fec8 lsr x8, x22, #3
* 10: 38796908 ldrb w8, [x8, x25] <-- trapping instruction

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#syz test: git://repo/address.git branch-or-commit-hash
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