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| author | Peter Collingbourne <pcc@google.com> | 2023-04-20 14:43:27 -0700 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2023-05-16 14:59:16 +0100 |
| commit | c4c597f1b367433c52c531dccd6859a39b4580fb (patch) | |
| tree | 2c18bd53a2f985bfea0b9f8695ba6bd0da5c7fb4 | |
| parent | 2efbafb91e12ff5a16cbafb0085e4c10c3fca493 (diff) | |
| download | linux-c4c597f1b367433c52c531dccd6859a39b4580fb.tar.gz | |
arm64: mte: Do not set PG_mte_tagged if tags were not initialized
The mte_sync_page_tags() function sets PG_mte_tagged if it initializes
page tags. Then we return to mte_sync_tags(), which sets PG_mte_tagged
again. At best, this is redundant. However, it is possible for
mte_sync_page_tags() to return without having initialized tags for the
page, i.e. in the case where check_swap is true (non-compound page),
is_swap_pte(old_pte) is false and pte_is_tagged is false. So at worst,
we set PG_mte_tagged on a page with uninitialized tags. This can happen
if, for example, page migration causes a PTE for an untagged page to
be replaced. If the userspace program subsequently uses mprotect() to
enable PROT_MTE for that page, the uninitialized tags will be exposed
to userspace.
Fix it by removing the redundant call to set_page_mte_tagged().
Fixes: e059853d14ca ("arm64: mte: Fix/clarify the PG_mte_tagged semantics")
Signed-off-by: Peter Collingbourne <pcc@google.com>
Cc: <stable@vger.kernel.org> # 6.1
Link: https://linux-review.googlesource.com/id/Ib02d004d435b2ed87603b858ef7480f7b1463052
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20230420214327.2357985-1-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>
| -rw-r--r-- | arch/arm64/kernel/mte.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index f5bcb0dc626738..7e89968bd28244 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -66,13 +66,10 @@ void mte_sync_tags(pte_t old_pte, pte_t pte) return; /* if PG_mte_tagged is set, tags have already been initialised */ - for (i = 0; i < nr_pages; i++, page++) { - if (!page_mte_tagged(page)) { + for (i = 0; i < nr_pages; i++, page++) + if (!page_mte_tagged(page)) mte_sync_page_tags(page, old_pte, check_swap, pte_is_tagged); - set_page_mte_tagged(page); - } - } /* ensure the tags are visible before the PTE is set */ smp_wmb(); |