On Sun, Jul 9, 2023 at 6:32 AM Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Sun, Jul 09, 2023 at 02:39:00PM +0200, Thorsten Leemhuis wrote: > > On 09.07.23 13:14, Greg Kroah-Hartman wrote: > > > From: Suren Baghdasaryan <surenb@xxxxxxxxxx> > > > > > > commit 2b4f3b4987b56365b981f44a7e843efa5b6619b9 upstream. > > > > > > Patch series "Avoid memory corruption caused by per-VMA locks", v4. > > > > > > A memory corruption was reported in [1] with bisection pointing to the > > > patch [2] enabling per-VMA locks for x86. Based on the reproducer > > > provided in [1] we suspect this is caused by the lack of VMA locking while > > > forking a child process. > > > [...] > > > > Question from someone that is neither a C nor a git expert -- and thus > > might say something totally stupid below (and thus maybe should not have > > sent this mail at all). > > > > But I have to wonder: is adding this patch to stable necessary given > > patch 8/8? > > > > FWIW, this change looks like this: > > > > > --- > > > kernel/fork.c | 6 ++++++ > > > 1 file changed, 6 insertions(+) > > > > > > --- a/kernel/fork.c > > > +++ b/kernel/fork.c > > > @@ -662,6 +662,12 @@ static __latent_entropy int dup_mmap(str > > > retval = -EINTR; > > > goto fail_uprobe_end; > > > } > > > +#ifdef CONFIG_PER_VMA_LOCK > > > + /* Disallow any page faults before calling flush_cache_dup_mm */ > > > + for_each_vma(old_vmi, mpnt) > > > + vma_start_write(mpnt); > > > + vma_iter_set(&old_vmi, 0); > > > +#endif > > > flush_cache_dup_mm(oldmm); > > > uprobe_dup_mmap(oldmm, mm); > > > /* > > > > But when I look at kernel/fork.c in mainline I can't see this bit. I > > also only see Linus' change (e.g. patch 8/8 in this series) when I look at > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/kernel/fork.c > > Look at 946c6b59c56d ("Merge tag 'mm-hotfixes-stable-2023-07-08-10-43' > of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") > > Where Linus manually dropped those #ifdefs. > > Hm, I'll leave them for now in 6.4.y as that is "safer", but if Suren > feels comfortable, I'll gladly take a patch from him to drop them in the > 6.4.y tree as well. Hi Greg, Give me a couple hours to get back to my computer. Linus took a different version of this patch and changed the description quite a bit. Once I'm home I can send you the patchset that was merged into his tree. Also let me know if you want to disable CONFIG_PER_VMA_LOCK in the stable branch (the patch called "[PATCH 6.4 1/8] mm: disable CONFIG_PER_VMA_LOCK until its fixed" which Linus did not take AFAIKT). Thanks, Suren. > > thanks, > > greg k-h
