On Sat, Apr 05, 2025 at 12:25:00PM -0400, Chuck Lever wrote: > On 4/5/25 3:43 AM, Paul Menzel wrote: > > Dear Greg, > > > > > > Thank you for replying on a Saturday. > > > > Am 05.04.25 um 09:29 schrieb Greg KH: > >> On Sat, Apr 05, 2025 at 08:32:13AM +0200, Paul Menzel wrote: > > > >>> Am 29.03.25 um 15:57 schrieb Chuck Lever: > >>>> On 3/29/25 8:17 AM, Takashi Iwai wrote: > >>>>> On Sun, 23 Feb 2025 09:53:10 +0100, Takashi Iwai wrote: > >>> > >>>>>> we received a bug report showing the regression on 6.13.1 kernel > >>>>>> against 6.13.0. The symptom is that Chrome and VSCode stopped > >>>>>> working > >>>>>> with Gnome Scaling, as reported on openSUSE Tumbleweed bug tracker > >>>>>> https://bugzilla.suse.com/show_bug.cgi?id=1236943 > >>>>>> > >>>>>> Quoting from there: > >>>>>> """ > >>>>>> I use the latest TW on Gnome with a 4K display and 150% > >>>>>> scaling. Everything has been working fine, but recently both Chrome > >>>>>> and VSCode (installed from official non-openSUSE channels) stopped > >>>>>> working with Scaling. > >>>>>> .... > >>>>>> I am using VSCode with: > >>>>>> `--enable-features=UseOzonePlatform --enable- > >>>>>> features=WaylandWindowDecorations --ozone-platform-hint=auto` and > >>>>>> for Chrome, I select `Preferred Ozone platform` == `Wayland`. > >>>>>> """ > >>>>>> > >>>>>> Surprisingly, the bisection pointed to the backport of the commit > >>>>>> b9b588f22a0c049a14885399e27625635ae6ef91 ("libfs: Use d_children list > >>>>>> to iterate simple_offset directories"). > >>>>>> > >>>>>> Indeed, the revert of this patch on the latest 6.13.4 was > >>>>>> confirmed to > >>>>>> fix the issue. Also, the reporter verified that the latest 6.14-rc > >>>>>> release is still affected, too. > >>>>>> > >>>>>> For now I have no concrete idea how the patch could break the > >>>>>> behavior > >>>>>> of a graphical application like the above. Let us know if you need > >>>>>> something for debugging. (Or at easiest, join to the bugzilla entry > >>>>>> and ask there; or open another bug report at whatever you like.) > >>>>>> > >>>>>> BTW, I'll be traveling tomorrow, so my reply will be delayed. > >>> > >>>>>> #regzbot introduced: b9b588f22a0c049a14885399e27625635ae6ef91 > >>>>>> #regzbot monitor: https://bugzilla.suse.com/show_bug.cgi?id=1236943 > >>>>> > >>>>> After all, this seems to be a bug in Chrome and its variant, which was > >>>>> surfaced by the kernel commit above: as the commit changes the > >>>>> directory enumeration, it also changed the list order returned from > >>>>> libdrm drmGetDevices2(), and it screwed up the application that worked > >>>>> casually beforehand. That said, the bug itself has been already > >>>>> present. The Chrome upstream tracker: > >>>>> https://issuetracker.google.com/issues/396434686 > >>>>> > >>>>> #regzbot invalid: problem has always existed on Chrome and related > >>>>> code > >>> > >>>> Thank you very much for your report and for chasing this to conclusion. > >>> Doesn’t marking this an invalid contradict Linux’ no regression > >>> policy to > >>> never break user space, so users can always update the Linux kernel? > >>> Shouldn’t this commit still be reverted, and another way be found > >>> keeping > >>> the old ordering? > >>> > >>> Greg, Sasha, in stable/linux-6.13.y the two commits below would need > >>> to be > >>> reverted: > >>> > >>> 180c7e44a18bbd7db89dfd7e7b58d920c44db0ca > >>> d9da7a68a24518e93686d7ae48937187a80944ea > >>> > >>> For stable/linux-6.12.y: > >>> > >>> 176d0333aae43bd0b6d116b1ff4b91e9a15f88ef > >>> 639b40424d17d9eb1d826d047ab871fe37897e76 > >> > >> Unless the changes are also reverted in Linus's tree, we'll be keeping > >> these in. Please work with the maintainers to resolve this in mainline > >> and we will be glad to mirror that in the stable trees as well. > > > > Commit b9b588f22a0c (libfs: Use d_children list to iterate simple_offset > > directories) does not have a Fixes: tag or Cc: stable@xxxxxxxxxxxxxxx. I > > do not understand, why it was applied to the stable series at all [1], > > and cannot be reverted when it breaks userspace? > I NACK'd the upstream revert because I expected an RCA before 6.14 > final (that didn't happen), and the Chrome issue was the only reported > problem and it was specific to a particular hardware configuration and > the /latest developer release/ of Chrome. Neither v6.14.0 nor a Chrome > developer release are going to be put in front of users who do not > expect to encounter issues. Exactly. > > Note that the libfs series addresses several issues. Commit b9b588f22a0c > itself addresses CVE-2024-46701 [1] (in v6.6). I did not add a "Cc: > stable" for commit b9b588f22a0c because it cannot be cherry picked to > apply to v6.6, it has to be manually adjusted to apply. > > The final RCA reported in [2] shows that there is nothing incorrect > about b9b588f22a0c. > > In addition, the next Chrome release will carry a fix for the clearly > incorrect library behavior -- applications cannot depend on the order > of directory entry iteration, because that can change arbitrarily, and > not just because of file system implementation quirks. You will note > that even after sorting the directory entries, the library still had > problems discovering the accelerated graphics device. > > Reverting now might follow the letter of the rule about "no regressions" > but IMHO moving forward from here seems to me to be the more > constructive approach. I agree.
