syzbot


general protection fault in zcomp_stream_get

Status: moderation: reported on 2025/07/30 08:16
Subsystems: block
[Documentation on labels]
Reported-by: syzbot+6e33d5041681e64acb21@syzkaller.appspotmail.com
First crash: 8d08h, last: 8d08h

Sample crash report:
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 17463 Comm: syz.0.2636 Not tainted 6.16.0-rc7-syzkaller-00120-g5f33ebd2018c #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:zcomp_stream_get+0x33/0xa0 drivers/block/zram/zcomp.c:114
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 9a 7f a6 fb e8 95 7f a6 fb 65 48 8b 1d c5 5a ba 0d <41> 80 3c 24 00 75 4f 48 03 5d 00 31 f6 48 89 df e8 b8 4b 6f 05 48
RSP: 0018:ffffc900045cf3a8 EFLAGS: 00010283
RAX: 0000000000000b80 RBX: ffff88812472d000 RCX: ffffc9000e891000
RDX: 0000000000080000 RSI: ffffffff8614d55b RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000006 R09: 7974742f00f22f2f
R10: 0000000000000000 R11: 0000000000000001 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffff888026c74c00 R15: ffffea0001a9eb00
FS:  00007fc9a11f06c0(0000) GS:ffff88812472d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f5dfff8 CR3: 000000006398a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 zram_write_page drivers/block/zram/zram_drv.c:1868 [inline]
 zram_bvec_write drivers/block/zram/zram_drv.c:1940 [inline]
 zram_bio_write drivers/block/zram/zram_drv.c:2381 [inline]
 zram_submit_bio+0xe1c/0x1e30 drivers/block/zram/zram_drv.c:2410
 __submit_bio+0x304/0x690 block/blk-core.c:644
 __submit_bio_noacct block/blk-core.c:690 [inline]
 submit_bio_noacct_nocheck+0x852/0xd30 block/blk-core.c:753
 submit_bio_noacct+0x50d/0x1eb0 block/blk-core.c:874
 __block_write_full_folio+0x735/0xe00 fs/buffer.c:1939
 block_write_full_folio+0x341/0x400 fs/buffer.c:2760
 blkdev_writepages+0xb8/0x140 block/fops.c:483
 do_writepages+0x27a/0x600 mm/page-writeback.c:2636
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 filemap_fdatawrite_wbc+0x104/0x160 mm/filemap.c:376
 __filemap_fdatawrite_range+0xb2/0xf0 mm/filemap.c:419
 file_write_and_wait_range+0xca/0x140 mm/filemap.c:794
 blkdev_fsync+0x6c/0xd0 block/fops.c:600
 vfs_fsync_range+0x136/0x220 fs/sync.c:187
 generic_write_sync include/linux/fs.h:3031 [inline]
 blkdev_write_iter+0x9cf/0xdf0 block/fops.c:784
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x6c4/0x1150 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/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc9a038e9a9
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:00007fc9a11f0038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc9a05b5fa0 RCX: 00007fc9a038e9a9
RDX: 00000000000000d0 RSI: 0000200000000040 RDI: 0000000000000007
RBP: 00007fc9a0410d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fc9a05b5fa0 R15: 00007ffec8e4ce28
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:zcomp_stream_get+0x33/0xa0 drivers/block/zram/zcomp.c:114
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 9a 7f a6 fb e8 95 7f a6 fb 65 48 8b 1d c5 5a ba 0d <41> 80 3c 24 00 75 4f 48 03 5d 00 31 f6 48 89 df e8 b8 4b 6f 05 48
RSP: 0018:ffffc900045cf3a8 EFLAGS: 00010283
RAX: 0000000000000b80 RBX: ffff88812472d000 RCX: ffffc9000e891000
RDX: 0000000000080000 RSI: ffffffff8614d55b RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000006 R09: 7974742f00f22f2f
R10: 0000000000000000 R11: 0000000000000001 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffff888026c74c00 R15: ffffea0001a9eb00
FS:  00007fc9a11f06c0(0000) GS:ffff88812482d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2edebff8 CR3: 000000006398a000 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 9a 7f a6 fb       	call   0xfba67fb1
  17:	e8 95 7f a6 fb       	call   0xfba67fb1
  1c:	65 48 8b 1d c5 5a ba 	mov    %gs:0xdba5ac5(%rip),%rbx        # 0xdba5ae9
  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 b8 4b 6f 05       	call   0x56f4bf1
  39:	48                   	rex.W

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/26 08:14 upstream 5f33ebd2018c fb8f743d .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto general protection fault in zcomp_stream_get
* Struck through repros no longer work on HEAD.