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From:   Bruno Thomsen <bruno.thomsen@gmail.com>
Date:   Fri, 6 Mar 2020 10:31:42 +0100
Message-ID: <CAH+2xPBuLsVjwStj4hQHDEbogKW+mXd2p66DG9X2F8nW+doyHw@mail.gmail.com>
Subject: Re: Still a pretty bad time on 5.4.6 with fuse_request_end.
To:     miklos@szeredi.hu, michael+lkml@stapelberg.ch
Cc:     fuse-devel@lists.sourceforge.net,
        Greg KH <gregkh@linuxfoundation.org>, kyle.leet@gmail.com,
        linux-fsdevel@vger.kernel.org,
        open list <linux-kernel@vger.kernel.org>,
        Bruno Thomsen <bth@kamstrup.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi,

First of all, sorry for the incorrect reply as I was not subscribed to
the mailing list.

A colleague and I have tested Miklos patch[1] on top of Fedora 31
5.5.7 kernel and it fixes a kernel oops[2] when using rootless
containers in Podman. Fix has been running for a few days now,
and the issue was normally reproducible within a few minutes.

Tested-by: Bruno Thomsen <bruno.thomsen@gmail.com>

/Bruno

[1] https://lore.kernel.org/linux-fsdevel/CAJfpegvBguKcNZk-p7sAtSuNH_7HfdCyYvo8Wh7X6P=hT=kPrA@mail.gmail.com/

[2] Oops when running podman workload.
kernel: BUG: kernel NULL pointer dereference, address: 0000000000000001
kernel: #PF: supervisor instruction fetch in kernel mode
kernel: #PF: error_code(0x0010) - not-present page
kernel: PGD 8000000e4cd85067 P4D 8000000e4cd85067 PUD e4cd80067 PMD 0
kernel: Oops: 0010 [#1] SMP PTI
kernel: CPU: 27 PID: 3422 Comm: fuse-overlayfs Not tainted
5.5.5-200.fc31.x86_64 #1
kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31
04/01/2014
kernel: RIP: 0010:0x1
kernel: Code: Bad RIP value.
kernel: RSP: 0018:ffffaa0d4196fc30 EFLAGS: 00010202
kernel: RAX: 0000000000000001 RBX: ffff8b5f344c2250 RCX: 0000000000000000
kernel: RDX: 0000000000000000 RSI: ffffaa0d4932fbb8 RDI: ffff8b65ac586800
kernel: RBP: ffff8b5f344c2240 R08: ffff8b5f344c22a0 R09: ffffaa0d4196fbd0
kernel: R10: ffff8b65a5c71888 R11: 0000000000000001 R12: ffff8b65ac586800
kernel: R13: 0000000000000001 R14: ffff8b65ab535dc0 R15: ffff8b5f344c2240
kernel: FS:  00007fb4239a7b80(0000) GS:ffff8b65b98c0000(0000)
knlGS:0000000000000000
kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
kernel: CR2: ffffffffffffffd7 CR3: 0000000e4cd38004 CR4: 0000000000360ee0
kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
kernel: Call Trace:
kernel:  ? fuse_request_end+0xbc/0x1f0 [fuse]
kernel:  ? fuse_dev_do_write+0x25e/0xe70 [fuse]
kernel:  ? lookup_fast+0xca/0x280
kernel:  ? fuse_dev_write+0x53/0x90 [fuse]
kernel:  ? do_iter_readv_writev+0x158/0x1d0
kernel:  ? do_iter_write+0x7d/0x190
kernel:  ? vfs_writev+0xa6/0xf0
kernel:  ? _copy_to_user+0x28/0x30
kernel:  ? readlink_copy+0x5a/0x80
kernel:  ? do_writev+0x6b/0x110
kernel:  ? do_syscall_64+0x5b/0x1c0
kernel:  ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
kernel: Modules linked in: tun ip6t_REJECT nf_reject_ipv6
ip6t_rpfilter ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_nat
ebtable_broute ip6table_nat ip6table_mangle ip6table_raw ip6table_>
kernel: CR2: 0000000000000001