[syzbot] [arm?] WARNING in do_sve_acc

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f7168591ebf Merge tag '6.7-rc5-smb3-client-fixes' of git:..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=108baf71e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=8cf3c4f966189832
dashboard link: https://syzkaller.appspot.com/bug?extid=95ffb6a83b20ea7f4f55
compiler: aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/384ffdcca292/non_bootable_disk-3f716859.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fc2a62c05f31/vmlinux-3f716859.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4dac83fca8af/Image-3f716859.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+95ffb6...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 16446 at arch/arm64/kernel/fpsimd.c:1394 do_sve_acc+0x6c/0x10c arch/arm64/kernel/fpsimd.c:1393
Modules linked in:
CPU: 0 PID: 16446 Comm: syz-executor.0 Not tainted 6.7.0-rc5-syzkaller-00134-g3f7168591ebf #0
Hardware name: linux,dummy-virt (DT)
pstate: 01400009 (nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
pc : do_sve_acc+0x6c/0x10c arch/arm64/kernel/fpsimd.c:1394
lr : do_sve_acc+0x5c/0x10c arch/arm64/kernel/fpsimd.c:1391
sp : ffff800082d1be60
x29: ffff800082d1be60 x28: fbff00000648af40 x27: 0000000000000000
x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
x23: 0000000080001000 x22: 0000ffffa04568d4 x21: 00000000ffffffff
x20: fbff00000648bec8 x19: fbff00000648af40 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
x8 : faff000029208888 x7 : 0000000000000000 x6 : 000000000000003f
x5 : 0000000000000040 x4 : 0000000000000000 x3 : 0000000000000001
x2 : 0000000000000000 x1 : ffff7ffffd52e000 x0 : 0000000000800000
Call trace:
do_sve_acc+0x6c/0x10c arch/arm64/kernel/fpsimd.c:1393
el0_sve_acc+0x2c/0x98 arch/arm64/kernel/entry-common.c:580
el0t_64_sync_handler+0xf4/0x12c arch/arm64/kernel/entry-common.c:708
el0t_64_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:595
---[ end trace 0000000000000000 ]---


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[Will Deacon]

[+Broonie and Mark R as I'm sure we've seen this one before, possibly
in a report from Naresh? Was it a QEMU issue?]

[Mark Brown]

On Wed, Jan 03, 2024 at 06:05:49PM +0000, Will Deacon wrote:
> [+Broonie and Mark R as I'm sure we've seen this one before, possibly
> in a report from Naresh? Was it a QEMU issue?]

It's been reported by the LKFT people, but it occurs with *extremely*
low frequency, there's no reproducer and nothing showed up from code
inspection by myself and Mark. The reports suggest it's been there
since ~v5.15 (that's the oldest stable it was seen in and Linaro do
still cover older), though Linaro's reports were conflating multiple
potentially related symptoms so it's a little unclear what exactly was
seen in what version.

I suspect to the extent it's qemu it's just that that's mostly where
people are exercising SVE. This was shown with a userspace with SVE
usage in glibc, I *think* that upgrading to a similar glibc version was
what started Linaro seeing things too based on the release dates for the
particular stable versions they mentioned but didn't get them to confirm
yet.

I *might've* been able to show something with current code just before
Christmas but the symptoms are a bit different, I was going to start
looking when I get back.

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

Indeed...

> > compiler: aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40