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authorCatalin Marinas <catalin.marinas@arm.com>2021-05-14 10:50:01 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2021-05-14 17:11:16 +0100
commit588a513d34257fdde95a9f0df0202e31998e85c6 (patch)
tree053e87f91afc329f6a187eae1a2e29ecaf6a3eed
parentaf44068c581c028fd9897ca75a10fa310d8fc449 (diff)
arm64: Fix race condition on PG_dcache_clean in __sync_icache_dcache()
To ensure that instructions are observable in a new mapping, the arm64 set_pte_at() implementation cleans the D-cache and invalidates the I-cache to the PoU. As an optimisation, this is only done on executable mappings and the PG_dcache_clean page flag is set to avoid future cache maintenance on the same page. When two different processes map the same page (e.g. private executable file or shared mapping) there's a potential race on checking and setting PG_dcache_clean via set_pte_at() -> __sync_icache_dcache(). While on the fault paths the page is locked (PG_locked), mprotect() does not take the page lock. The result is that one process may see the PG_dcache_clean flag set but the I/D cache maintenance not yet performed. Avoid test_and_set_bit(PG_dcache_clean) in favour of separate test_bit() and set_bit(). In the rare event of a race, the cache maintenance is done twice. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: <stable@vger.kernel.org> Cc: Will Deacon <will@kernel.org> Cc: Steven Price <steven.price@arm.com> Reviewed-by: Steven Price <steven.price@arm.com> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20210514095001.13236-1-catalin.marinas@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
-rw-r--r--arch/arm64/mm/flush.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
index ac485163a4a7..6d44c028d1c9 100644
--- a/arch/arm64/mm/flush.c
+++ b/arch/arm64/mm/flush.c
@@ -55,8 +55,10 @@ void __sync_icache_dcache(pte_t pte)
{
struct page *page = pte_page(pte);
- if (!test_and_set_bit(PG_dcache_clean, &page->flags))
+ if (!test_bit(PG_dcache_clean, &page->flags)) {
sync_icache_aliases(page_address(page), page_size(page));
+ set_bit(PG_dcache_clean, &page->flags);
+ }
}
EXPORT_SYMBOL_GPL(__sync_icache_dcache);