On Wed, Jul 5, 2023 at 1:25 PM Peter Xu <peterx@xxxxxxxxxx> wrote: > > On Wed, Jul 05, 2023 at 10:22:27AM -0700, Suren Baghdasaryan wrote: > > On Wed, Jul 5, 2023 at 10:16 AM David Hildenbrand <david@xxxxxxxxxx> wrote: > > > > > > On 05.07.23 19:12, Suren Baghdasaryan wrote: > > > > A memory corruption was reported in [1] with bisection pointing to the > > > > patch [2] enabling per-VMA locks for x86. > > > > Disable per-VMA locks config to prevent this issue while the problem is > > > > being investigated. This is expected to be a temporary measure. > > > > > > > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=217624 > > > > [2] https://lore.kernel.org/all/20230227173632.3292573-30-surenb@xxxxxxxxxx > > > > > > > > Reported-by: Jiri Slaby <jirislaby@xxxxxxxxxx> > > > > Closes: https://lore.kernel.org/all/dbdef34c-3a07-5951-e1ae-e9c6e3cdf51b@xxxxxxxxxx/ > > > > Reported-by: Jacob Young <jacobly.alt@xxxxxxxxx> > > > > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217624 > > > > Fixes: 0bff0aaea03e ("x86/mm: try VMA lock-based page fault handling first") > > > > Cc: stable@xxxxxxxxxxxxxxx > > > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> > > > > --- > > > > mm/Kconfig | 3 ++- > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/mm/Kconfig b/mm/Kconfig > > > > index 09130434e30d..0abc6c71dd89 100644 > > > > --- a/mm/Kconfig > > > > +++ b/mm/Kconfig > > > > @@ -1224,8 +1224,9 @@ config ARCH_SUPPORTS_PER_VMA_LOCK > > > > def_bool n > > > > > > > > config PER_VMA_LOCK > > > > - def_bool y > > > > + bool "Enable per-vma locking during page fault handling." > > > > depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP > > > > + depends on BROKEN > > > > help > > > > Allow per-vma locking during page fault handling. > > > > > > > Do we have any testing results (that don't reveal other issues :) ) for > > > patch #1? Not sure if we really want to mark it broken if patch #1 fixes > > > the issue. > > > > I tested the fix using the only reproducer provided in the reports > > plus kernel compilation and my fork stress test. All looked good and > > stable but I don't know if other reports had the same issue or > > something different. > > The commit log seems slightly confusing. It mostly says the bug was still > not solved, but I assume patch 1 is the current "fix", it's just not clear > whether there's any other potential issues? > > According to the stable tree rules: > > - It must fix a problem that causes a build error (but not for things > marked CONFIG_BROKEN), an oops, a hang, data corruption, a real > security issue, or some "oh, that's not good" issue. In short, something > critical. > > I think it means vma lock will never be fixed in 6.4, and it can't (because > after this patch it'll be BROKEN, and this patch copies stable, and we > can't fix BROKEN things in stables). I was hoping we could re-enable VMA locks in 6.4 once we get more confirmations that the problem is gone. Is that not possible once the BROKEN dependency is merged? > > Totally no problem I see, just to make sure this is what you wanted.. > > There'll still try to be a final fix, am I right? As IIRC allowing page > faults during fork() is one of the major goals of vma lock. I think we can further optimize the locking rules here (see discussion in https://lore.kernel.org/all/20230703182150.2193578-1-surenb@xxxxxxxxxx/) but for now we want the most effective and simple way to fix the memory corruption problem. Thanks, Suren. > > Thanks, > > -- > Peter Xu >
