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. thanks, greg k-h
