The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 2efbafb91e12ff5a16cbafb0085e4c10c3fca493 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023052235-cut-gulp-ad69@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

2efbafb91e12 ("arm64: Also reset KASAN tag if page is not PG_mte_tagged") e74a68468062 ("arm64: Reset KASAN tag in copy_highpage with HW tags only") d77e59a8fccd ("arm64: mte: Lock a page for MTE tag initialisation") e059853d14ca ("arm64: mte: Fix/clarify the PG_mte_tagged semantics")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2efbafb91e12ff5a16cbafb0085e4c10c3fca493 Mon Sep 17 00:00:00 2001 From: Peter Collingbourne pcc@google.com Date: Thu, 20 Apr 2023 14:09:45 -0700 Subject: [PATCH] arm64: Also reset KASAN tag if page is not PG_mte_tagged

Consider the following sequence of events:

1) A page in a PROT_READ|PROT_WRITE VMA is faulted. 2) Page migration allocates a page with the KASAN allocator, causing it to receive a non-match-all tag, and uses it to replace the page faulted in 1. 3) The program uses mprotect() to enable PROT_MTE on the page faulted in 1.

As a result of step 3, we are left with a non-match-all tag for a page with tags accessible to userspace, which can lead to the same kind of tag check faults that commit e74a68468062 ("arm64: Reset KASAN tag in copy_highpage with HW tags only") intended to fix.

The general invariant that we have for pages in a VMA with VM_MTE_ALLOWED is that they cannot have a non-match-all tag. As a result of step 2, the invariant is broken. This means that the fix in the referenced commit was incomplete and we also need to reset the tag for pages without PG_mte_tagged.

Fixes: e5b8d9218951 ("arm64: mte: reset the page tag in page->flags") Cc: stable@vger.kernel.org # 5.15 Link: https://linux-review.googlesource.com/id/I7409cdd41acbcb215c2a7417c1e50d37b8... Signed-off-by: Peter Collingbourne pcc@google.com Reviewed-by: Catalin Marinas catalin.marinas@arm.com Link: https://lore.kernel.org/r/20230420210945.2313627-1-pcc@google.com Signed-off-by: Will Deacon will@kernel.org

diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c index 4aadcfb01754..a7bb20055ce0 100644 --- a/arch/arm64/mm/copypage.c +++ b/arch/arm64/mm/copypage.c @@ -21,9 +21,10 @@ void copy_highpage(struct page *to, struct page *from)

copy_page(kto, kfrom);

+ if (kasan_hw_tags_enabled()) + page_kasan_tag_reset(to); + if (system_supports_mte() && page_mte_tagged(from)) { - if (kasan_hw_tags_enabled()) - page_kasan_tag_reset(to); /* It's a new page, shouldn't have been tagged yet */ WARN_ON_ONCE(!try_page_mte_tagging(to)); mte_copy_page_tags(kto, kfrom);