On Wed 03 Mar 2021 22:50:44 GMT Shengjing Zhu wrote: > On Wed, Mar 03, 2021 at 11:30:20AM +0100, Nicolas Schier wrote: > > On Wed 03 Mar 2021 17:33:16 GMT Shengjing Zhu write: > > > > > > On Wed, Mar 3, 2021 at 3:40 PM Nicolas Schier <nico...@fjasle.eu> wrote: > > > > > [2]: > > > > > https://lore.kernel.org/linux-unionfs/CAJfpegsiuf8ib5cvVrr=zhz+xu7bmmtt2eyapseudmpcrbu...@mail.gmail.com/T/#t > > > > > > > > The overlay fs patchset [2] has been merged and with v5.10.13 (tested > > > > on linux-image-5.10.0-3-arm64) the issue is no more reproducible for > > > > me. Might you want to re-check on your site? > > > > > > > > > > If I understand correctly, the upstream patch is merged into the v5.11 > > > tree. > > > > Sorry. Yes, you're right. > > > > > And I still can reproduce the error on the Debian v5.10 kernel. > > > > That confuses me quite a bit. I did it once again on an ext4 mount > > (still the 5.10.0-3-arm64 kernel): > > > > nsc@lillesand:/tmp$ cat > > /sys/module/overlay/parameters/permit_mounts_in_userns > > Y > > nsc@lillesand:/tmp$ mkdir -p test/lower/a test/merged test/upper test/work > > nsc@lillesand:/tmp$ uname -a | tee test/lower/a/a > > Linux lillesand 5.10.0-3-arm64 #1 SMP Debian 5.10.13-1 (2021-02-06) > > aarch64 GNU/Linux > > nsc@lillesand:/tmp$ unshare -m -U -r > > root@lillesand:/tmp# mount -t overlay -o > > rw,lowerdir=/tmp/test/lower,upperdir=/tmp/test/upper,workdir=/tmp/test/work > > overlay /tmp/test/merged > > root@lillesand:/tmp# rm -rf test/merged/a > > root@lillesand:/tmp# find test -ls > > 1597776 4 drwxr-xr-x 6 root root 4096 mars 3 08:24 > > test > > 1973978 4 drwxr-xr-x 2 root root 4096 mars 3 08:27 > > test/upper > > 2099881 0 c--------- 1 root root 0, 0 mars 3 08:27 > > test/upper/a > > 1973978 4 drwxr-xr-x 1 root root 4096 mars 3 08:27 > > test/merged > > 1714388 4 drwxr-xr-x 3 root root 4096 mars 3 08:24 > > test/lower > > 1714389 4 drwxr-xr-x 2 root root 4096 mars 3 08:27 > > test/lower/a > > 1714393 4 -rw-r--r-- 1 root root 86 mars 3 10:48 > > test/lower/a/a > > 1973979 4 drwxr-xr-x 3 root root 4096 mars 3 10:48 > > test/work > > 2099880 4 d--------- 2 root root 4096 mars 3 10:48 > > test/work/work > > root@lillesand:/tmp# > > > zsj@debian:~$ cat /sys/module/overlay/parameters/permit_mounts_in_userns > Y > zsj@debian:~/t$ mkdir -p test/lower/a test/merged test/upper test/work > zsj@debian:~/t$ uname -a | tee test/lower/a/a > Linux debian 5.10.0-3-amd64 #1 SMP Debian 5.10.13-1 (2021-02-06) x86_64 > GNU/Linux > zsj@debian:~/t$ unshare -m -U -r > root@debian:~/t# mount -t overlay -o > rw,lowerdir=./test/lower,upperdir=./test/upper,workdir=./test/work overlay > ./test/merged/ > root@debian:~/t# rm -rf ./test/merged/a > rm: cannot remove './test/merged/a': Input/output error > root@debian:~/t# find test -ls > 7350352 4 drwxr-xr-x 6 root root 4096 Mar 3 22:44 test > 7351341 4 drwxr-xr-x 3 root root 4096 Mar 3 22:44 > test/lower > 7353492 4 drwxr-xr-x 2 root root 4096 Mar 3 22:44 > test/lower/a > 7356441 4 -rw-r--r-- 1 root root 82 Mar 3 22:44 > test/lower/a/a > 7356069 4 drwxr-xr-x 3 root root 4096 Mar 3 22:45 > test/work > 7358324 4 d--------- 2 root root 4096 Mar 3 22:45 > test/work/work > 7358564 0 c--------- 2 root root 0, 0 Mar 3 22:45 > test/work/work/#4 > 7354400 4 drwxr-xr-x 3 root root 4096 Mar 3 22:44 > test/upper > 7358563 4 drwxr-xr-x 2 root root 4096 Mar 3 22:45 > test/upper/a > 7358564 0 c--------- 2 root root 0, 0 Mar 3 22:45 > test/upper/a/a > 7354400 4 drwxr-xr-x 1 root root 4096 Mar 3 22:44 > test/merged > 7353492 4 drwxr-xr-x 1 root root 4096 Mar 3 22:45 > test/merged/a > > > Do you see any kernel log message from overlay fs? Might it depend on > > the underlying filesystem? Can you create a white-out char dev node > > manually? > > > > [1215353.859717] Setting dangerous option permit_mounts_in_userns - tainting > kernel > [1215353.859841] overlayfs: overlayfs: Allowing overlay mounts in user > namespaces bears security risks > [1215425.416543] overlayfs: upper fs does not support xattr, falling back to > index=off and metacopy=off. > > The underlying fs is ext4. > > zsj@debian:~/t$ mount|grep nvme > /dev/nvme0n1p2 on / type ext4 (rw,relatime,errors=remount-ro) > /dev/nvme0n1p4 on /home type ext4 (rw,relatime) > /dev/nvme0n1p1 on /boot/efi type vfat > (rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro) > > I don't know how to test "create a white-out char dev node manually". > > Thanks
thanks for re-validation. I can reproduce the issue exactly on amd64
system, but not on arm64. It's really strange, also enabling dynamic
debug output does not reveal anything useful. I guess it would be good
to dig into the related kernel code to get some deeper understanding, I
hope to get start examining a bit in the upcoming weekend.
Kind regards,
Nicolas
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