[syzbot] [overlayfs?] WARNING in ovl_copy_up_file

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 707081b61156 Merge branch 'for-next/core', remote-tracking..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=1785a859180000
kernel config: https://syzkaller.appspot.com/x/.config?x=caeac3f3565b057a
dashboard link: https://syzkaller.appspot.com/bug?extid=3abd99031b42acf367ef
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1115ada6180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1626870a180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6cad68bf7532/disk-707081b6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1a27e5400778/vmlinux-707081b6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/67dfc53755d0/Image-707081b6.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3abd99...@syzkaller.appspotmail.com

evm: overlay not supported
------------[ cut here ]------------
WARNING: CPU: 0 PID: 6187 at fs/overlayfs/copy_up.c:239 ovl_copy_up_file+0x624/0x674 fs/overlayfs/copy_up.c:330
Modules linked in:
CPU: 0 PID: 6187 Comm: syz-executor136 Not tainted 6.8.0-rc7-syzkaller-g707081b61156 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : ovl_copy_up_file+0x624/0x674 fs/overlayfs/copy_up.c:330
lr : ovl_verify_area fs/overlayfs/copy_up.c:239 [inline]
lr : ovl_copy_up_file+0x620/0x674 fs/overlayfs/copy_up.c:330
sp : ffff800097997180
x29: ffff800097997280 x28: 00000000fffffffb x27: ffff700012f32e3c
x26: 0000000000800000 x25: 0000000000800000 x24: ffff800097997240
x23: ffff800097997220 x22: ffffffffffa64000 x21: ffffffffffa64000
x20: ffff0000d9fc1900 x19: dfff800000000000 x18: 1ffff00012f32dee
x17: ffff80008ec9d000 x16: ffff80008ad6b1c0 x15: 0000000000000001
x14: 1fffe0001b9177f2 x13: 0000000000000000 x12: 0000000000000000
x11: 0000000000000001 x10: 0000000000ff0100 x9 : 0000000000000000
x8 : ffff0000d7568000 x7 : ffff80008108d924 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff80008031a200
x2 : 00000ffffffff000 x1 : ffffffffffa64000 x0 : ffffffffffffffff
Call trace:
ovl_copy_up_file+0x624/0x674 fs/overlayfs/copy_up.c:330
ovl_copy_up_tmpfile fs/overlayfs/copy_up.c:863 [inline]
ovl_do_copy_up fs/overlayfs/copy_up.c:976 [inline]
ovl_copy_up_one fs/overlayfs/copy_up.c:1168 [inline]
ovl_copy_up_flags+0x16d0/0x3694 fs/overlayfs/copy_up.c:1223
ovl_copy_up+0x24/0x34 fs/overlayfs/copy_up.c:1263
ovl_setattr+0xfc/0x4e4 fs/overlayfs/inode.c:41
notify_change+0x9d4/0xc8c fs/attr.c:499
chmod_common+0x23c/0x418 fs/open.c:648
do_fchmodat fs/open.c:696 [inline]
__do_sys_fchmodat fs/open.c:715 [inline]
__se_sys_fchmodat fs/open.c:712 [inline]
__arm64_sys_fchmodat+0x118/0x1dc fs/open.c:712
__invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152
el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
irq event stamp: 862
hardirqs last enabled at (861): [<ffff8000831abcb4>] percpu_counter_add_batch+0x210/0x30c lib/percpu_counter.c:102
hardirqs last disabled at (862): [<ffff80008ad66988>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:470
softirqs last enabled at (62): [<ffff80008002189c>] softirq_handle_end kernel/softirq.c:399 [inline]
softirqs last enabled at (62): [<ffff80008002189c>] __do_softirq+0xac8/0xce4 kernel/softirq.c:582
softirqs last disabled at (53): [<ffff80008002ab48>] ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:81
---[ end trace 0000000000000000 ]---


---
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[Amir Goldstein]

On Wed, Mar 13, 2024 at 12:23 PM syzbot
<syzbot+3abd99...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 707081b61156 Merge branch 'for-next/core', remote-tracking..
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=1785a859180000
> kernel config: https://syzkaller.appspot.com/x/.config?x=caeac3f3565b057a
> dashboard link: https://syzkaller.appspot.com/bug?extid=3abd99031b42acf367ef
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1115ada6180000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1626870a180000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/6cad68bf7532/disk-707081b6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/1a27e5400778/vmlinux-707081b6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/67dfc53755d0/Image-707081b6.gz.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+3abd99...@syzkaller.appspotmail.com
>
> evm: overlay not supported
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 6187 at fs/overlayfs/copy_up.c:239 ovl_copy_up_file+0x624/0x674 fs/overlayfs/copy_up.c:330

Miklos,

The WARN_ON that I put in ovl_verify_area() may be too harsh.
I think they can happen if lower file is changed (i_size) while file is being
copied up after reading i_size into the copy length and this could be
the case with this syzbot reproducer that keeps mounting overlayfs
instances over same path.

Should probably demote those WARN_ON to just returning EIO?

Thanks,
Amir.

[Miklos Szeredi]

On Wed, 13 Mar 2024 at 21:55, Amir Goldstein <amir...@gmail.com> wrote:

> The WARN_ON that I put in ovl_verify_area() may be too harsh.
> I think they can happen if lower file is changed (i_size) while file is being
> copied up after reading i_size into the copy length and this could be
> the case with this syzbot reproducer that keeps mounting overlayfs
> instances over same path.
>
> Should probably demote those WARN_ON to just returning EIO?

Sounds good.

Thanks,
Miklos

[Amir Goldstein]

On Wed, Mar 13, 2024 at 12:23 PM syzbot
<syzbot+3abd99...@syzkaller.appspotmail.com> wrote:
>

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 707081b61156 Merge branch 'for-next/core', remote-tracking..
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=1785a859180000
> kernel config: https://syzkaller.appspot.com/x/.config?x=caeac3f3565b057a
> dashboard link: https://syzkaller.appspot.com/bug?extid=3abd99031b42acf367ef
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1115ada6180000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1626870a180000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/6cad68bf7532/disk-707081b6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/1a27e5400778/vmlinux-707081b6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/67dfc53755d0/Image-707081b6.gz.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+3abd99...@syzkaller.appspotmail.com
>

#syz test: https://github.com/amir73il/linux ovl-fixes

Thanks,
Amir.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+3abd99...@syzkaller.appspotmail.com

Tested on:

commit: a8d73a85 ovl: relax WARN_ON in ovl_verify_area()
git tree: https://github.com/amir73il/linux ovl-fixes
console output: https://syzkaller.appspot.com/x/log.txt?x=14d627b6180000
kernel config: https://syzkaller.appspot.com/x/.config?x=2271d60b0617d474

dashboard link: https://syzkaller.appspot.com/bug?extid=3abd99031b42acf367ef
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.