[syzbot] [ide?] UBSAN: shift-out-of-bounds in ata_qc_issue

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ca4ee40bf13d Partly revert "drm/hyperv: Remove reference t..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13c6c722580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a771bfd268751cd6
dashboard link: https://syzkaller.appspot.com/bug?extid=1f77b8ca15336fff21ff
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-ca4ee40b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c714adf37ddd/vmlinux-ca4ee40b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4d56cd9f6175/bzImage-ca4ee40b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1f77b8...@syzkaller.appspotmail.com

------------[ cut here ]------------
UBSAN: shift-out-of-bounds in drivers/ata/libata-core.c:5166:24
shift exponent 4210818301 is too large for 64-bit type 'long long unsigned int'
CPU: 2 UID: 0 PID: 1282 Comm: kworker/2:1H Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_highpri ata_scsi_deferred_qc_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
ubsan_epilogue+0xa/0x30 lib/ubsan.c:233
__ubsan_handle_shift_out_of_bounds+0x279/0x2a0 lib/ubsan.c:494
ata_qc_issue.cold+0x38/0x9f drivers/ata/libata-core.c:5166
ata_scsi_deferred_qc_work+0x154/0x1f0 drivers/ata/libata-scsi.c:1679
process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
process_scheduled_works kernel/workqueue.c:3358 [inline]
worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
kthread+0x370/0x450 kernel/kthread.c:467
ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
---[ end trace ]---
Kernel panic - not syncing: UBSAN: panic_on_warn set ...
CPU: 2 UID: 0 PID: 1282 Comm: kworker/2:1H Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_highpri ata_scsi_deferred_qc_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
vpanic+0x552/0x970 kernel/panic.c:650
panic+0xd1/0xe0 kernel/panic.c:787
check_panic_on_warn kernel/panic.c:524 [inline]
check_panic_on_warn.cold+0x19/0x34 kernel/panic.c:519
__ubsan_handle_shift_out_of_bounds+0x279/0x2a0 lib/ubsan.c:494
ata_qc_issue.cold+0x38/0x9f drivers/ata/libata-core.c:5166
ata_scsi_deferred_qc_work+0x154/0x1f0 drivers/ata/libata-scsi.c:1679
process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
process_scheduled_works kernel/workqueue.c:3358 [inline]
worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
kthread+0x370/0x450 kernel/kthread.c:467
ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[Niklas Cassel]

On Tue, Feb 17, 2026 at 12:55:35PM -0800, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: ca4ee40bf13d Partly revert "drm/hyperv: Remove reference t..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13c6c722580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=a771bfd268751cd6
> dashboard link: https://syzkaller.appspot.com/bug?extid=1f77b8ca15336fff21ff
> compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-ca4ee40b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/c714adf37ddd/vmlinux-ca4ee40b.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/4d56cd9f6175/bzImage-ca4ee40b.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+1f77b8...@syzkaller.appspotmail.com
>
> ------------[ cut here ]------------
> UBSAN: shift-out-of-bounds in drivers/ata/libata-core.c:5166:24
> shift exponent 4210818301 is too large for 64-bit type 'long long unsigned int'

4210818301 is 0xfafbfcfd

0xfafbfcfd is ATA_TAG_POISON.

ATA_TAG_POISON is set by ata_qc_free(), so it appears that
ata_scsi_deferred_qc_work() is trying to issue a QC that has
already been freed.


Kind regards,
Niklas