APPLIED: [SRU][R][PATCH 0/1] Installer fails internally with a RSync error due to page fault

[Mehmet Basaran]

Applied to resolute:linux master-next branch. Thanks.

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AceLan Kao via kernel-team <kernel-team at lists.ubuntu.com> writes:

> From: "Chia-Lin Kao (AceLan)" <acelan.kao at canonical.com>
>
> BugLink: https://bugs.launchpad.net/bugs/2150640
>
> [Impact]
> Ubuntu installer randomly fails when rsync calls getdents64() on overlayfs-mounted
> directories. The overlay filesystem module returns a bogus non-zero error code that
> propagates up to rsync, causing the transfer to abort.
>
> Error log:
>
> BUG: unable to handle page fault for address: ffffffff825c9290
> Oops: Oops: 0000 [#2] SMP NOPTI
> ovl_iterate_merged+0x1d8/0x2b0 [overlay]
>
> rsync then fails with:
>
> rsync: connection unexpectedly closed (0 bytes received so far) [Receiver]
> rsync error: error in rsync protocol data stream (code 12) at io.c(232)
>
> Affects installation on QEMU VMs and physical hardware with various CPU/GPU configs
> (AMD, Intel iGPU). Hits at random intervals.
>
> [Fix]
> Only compute PTR_ERR(cache) on the error path in ovl_iterate_merged().
> The bug was storing PTR_ERR(cache) before checking IS_ERR(cache), so on
> success the truncated pointer value was returned as a false error.
>
> Upstream in v7.1-rc7.
> Commit: 1711b6ed6953cee5940ca4c3a6e77f1b3798cee2
>
> [Test Plan]
> Mount an overlayfs and run rsync:
>
> $ mkdir -p /tmp/lower /tmp/upper /tmp/work /tmp/mnt
> $ mount -t overlay overlay -o lowerdir=/tmp/lower,upperdir=/tmp/upper,\
> workdir=/tmp/work /tmp/mnt
> $ echo "test" > /tmp/lower/file.txt
> $ rsync -aXHAS /tmp/mnt/ /tmp/dest/
>
> Without patch: rsync fails with connection error or page fault in dmesg
> With patch: rsync completes successfully
>
> [Where problems could occur]
> Could break overlayfs directory iteration on any read.
>
> If the fix has a logic error, overlay readdir could return false errors
> or skip valid entries. Applications using rsync or other tools that do
> directory traversal would fail unexpectedly.
>
> Nirmoy Das (1):
>   ovl: keep err zero after successful ovl_cache_get()
>
>  fs/overlayfs/readdir.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> --
> 2.53.0
>
>
> --
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team
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