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

[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+1f77b8ca15336fff21ff@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ------------[ 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