On Sun, Jul 09, 2023 at 08:24:29PM +0000, Suren Baghdasaryan wrote:
On Sun, Jul 9, 2023 at 7:53 PM Suren Baghdasaryan surenb@google.com wrote:
On Sun, Jul 9, 2023 at 7:48 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Sun, Jul 09, 2023 at 09:04:09AM -0700, Suren Baghdasaryan wrote:
On Sun, Jul 9, 2023 at 6:32 AM Greg Kroah-Hartman gregkh@linuxfoundation.org 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@google.com > > 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/kerne...
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).
No rush, you can do this on Monday.
I took the patches that Linus added to his tree already into the stable 6.4.y tree, and it's in the -rc release I pushed out a few hours ago.
I just checked your stable master branch and it's perfectly in sync with Linus' tree.
So if you want to look at the -rc release, that would be great, the full list of patches can be seen here: https://lore.kernel.org/r/20230709111345.297026264@linuxfoundation.org
Let me sync git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git to see what's happening there.
Ok, I'm looking at the linux-6.4.y branch in git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
This patch is not needed (obsolete): 32d458fa68fe ("fork: lock VMAs of the parent process when forking")
Ok, I can drop that.
Patch fb49c455323f ("fork: lock VMAs of the parent process when forking, again") can be renamed into "fork: lock VMAs of the parent process when forking" as its original.
Yes, I had to rename it, git doesn't like patches with identical names.
Patch 11eaf9aa0699 ("mm: disable CONFIG_PER_VMA_LOCK until its fixed") was removed in Linus' tree, see comment in 946c6b59c56dc6e7d8364a8959cb36bf6d10bc37 saying: "The merge undoes the disabling of the CONFIG_PER_VMA_LOCK feature, since it was all hopefully fixed in mainline.". Unless you want to keep CONFIG_PER_VMA_LOCK disabled in the stable tree, that patch should also be dropped.
Ok, let me drop this too.
I'll push out a -rc2 with these changes, let me go work on it now...
thanks,
gre gk-h