[syzbot] [block?] general protection fault in zcomp_stream_get

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7a0892d2836e Merge tag 'pci-v6.18-fixes-5' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12152914580000
kernel config: https://syzkaller.appspot.com/x/.config?x=19d831c6d0386a9c
dashboard link: https://syzkaller.appspot.com/bug?extid=16a8410141ca18c0d963
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a45e159158b8/disk-7a0892d2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/846d1b2a57ec/vmlinux-7a0892d2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8b608296ff12/bzImage-7a0892d2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+16a841...@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 UID: 0 PID: 14292 Comm: syz.1.2163 Tainted: G U W L XTNJ syzkaller #0 PREEMPT(full)
Tainted: [U]=USER, [W]=WARN, [L]=SOFTLOCKUP, [X]=AUX, [T]=RANDSTRUCT, [N]=TEST, [J]=FWCTL
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:zcomp_stream_get+0x33/0xa0 drivers/block/zram/zcomp.c:113
Code: 00 00 00 00 fc ff df 41 54 55 48 89 fd 53 49 89 ec 49 c1 ec 03 4d 01 ec e8 5a b8 d5 fb e8 55 b8 d5 fb 65 48 8b 1d 15 90 ba 0d <41> 80 3c 24 00 75 4f 48 03 5d 00 31 f6 48 89 df e8 e8 92 78 05 48
RSP: 0018:ffffc90003baf488 EFLAGS: 00010283
RAX: 0000000000000516 RBX: ffff888124b0d000 RCX: ffffc9000ae99000
RDX: 0000000000080000 RSI: ffffffff85e6a00b RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000006 R09: 7277682f7665642f
R10: eb9cce1e473f4118 R11: 0000000000000001 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffff888142f2fc00 R15: ffffea0002067280
FS: 00007f1de6ff66c0(0000) GS:ffff888124b0d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b311f7ff8 CR3: 000000004f02c000 CR4: 00000000003526f0
Call Trace:
<TASK>
zram_write_page drivers/block/zram/zram_drv.c:1859 [inline]
zram_bvec_write drivers/block/zram/zram_drv.c:1932 [inline]
zram_bio_write drivers/block/zram/zram_drv.c:2373 [inline]
zram_submit_bio+0xdd4/0x1df0 drivers/block/zram/zram_drv.c:2402
__submit_bio+0x304/0x690 block/blk-core.c:646
__submit_bio_noacct block/blk-core.c:692 [inline]
submit_bio_noacct_nocheck+0x75c/0xc10 block/blk-core.c:757
submit_bio_noacct+0x5bd/0x1f60 block/blk-core.c:879
submit_bio_wait+0x110/0x250 block/bio.c:1388
__blkdev_direct_IO_simple+0x488/0x860 block/fops.c:99
blkdev_direct_IO+0xcc6/0x2100 block/fops.c:435
blkdev_direct_write block/fops.c:726 [inline]
blkdev_write_iter+0x703/0xe00 block/fops.c:794
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x7d3/0x11d0 fs/read_write.c:686
ksys_write+0x12a/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1de8d8f6c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1de6ff6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1de8fe5fa0 RCX: 00007f1de8d8f6c9
RDX: 000000100000a3d9 RSI: 0000200000000400 RDI: 0000000000000003
RBP: 00007f1de8e11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1de8fe6038 R14: 00007f1de8fe5fa0 R15: 00007ffd527f5948
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:zcomp_stream_get+0x33/0xa0 drivers/block/zram/zcomp.c:113
Code: 00 00 00 00 fc ff df 41 54 55 48 89 fd 53 49 89 ec 49 c1 ec 03 4d 01 ec e8 5a b8 d5 fb e8 55 b8 d5 fb 65 48 8b 1d 15 90 ba 0d <41> 80 3c 24 00 75 4f 48 03 5d 00 31 f6 48 89 df e8 e8 92 78 05 48
RSP: 0018:ffffc90003baf488 EFLAGS: 00010283
RAX: 0000000000000516 RBX: ffff888124b0d000 RCX: ffffc9000ae99000
RDX: 0000000000080000 RSI: ffffffff85e6a00b RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000006 R09: 7277682f7665642f
R10: eb9cce1e473f4118 R11: 0000000000000001 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffff888142f2fc00 R15: ffffea0002067280
FS: 00007f1de6ff66c0(0000) GS:ffff888124b0d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055a02d54d950 CR3: 000000004f02c000 CR4: 00000000003526f0
----------------
Code disassembly (best guess), 6 bytes skipped:
0: df 41 54 filds 0x54(%rcx)
3: 55 push %rbp
4: 48 89 fd mov %rdi,%rbp
7: 53 push %rbx
8: 49 89 ec mov %rbp,%r12
b: 49 c1 ec 03 shr $0x3,%r12
f: 4d 01 ec add %r13,%r12
12: e8 5a b8 d5 fb call 0xfbd5b871
17: e8 55 b8 d5 fb call 0xfbd5b871
1c: 65 48 8b 1d 15 90 ba mov %gs:0xdba9015(%rip),%rbx # 0xdba9039
23: 0d
* 24: 41 80 3c 24 00 cmpb $0x0,(%r12) <-- trapping instruction
29: 75 4f jne 0x7a
2b: 48 03 5d 00 add 0x0(%rbp),%rbx
2f: 31 f6 xor %esi,%esi
31: 48 89 df mov %rbx,%rdi
34: e8 e8 92 78 05 call 0x5789321
39: 48 rex.W


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Sergey Senozhatsky]

On (25/11/14 17:36), syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 7a0892d2836e Merge tag 'pci-v6.18-fixes-5' of git://git.ke..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12152914580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=19d831c6d0386a9c
> dashboard link: https://syzkaller.appspot.com/bug?extid=16a8410141ca18c0d963
> compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>
> Unfortunately, I don't have any reproducer for this issue yet.

This will be difficult to understand w/o a reproducer.
I'll try to look at it, but it doesn't make a lot of sense
to me right now: raw_cpu_ptr(comp->stream) should work.