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author | Catalin Marinas <catalin.marinas@arm.com> | 2021-05-14 12:50:01 +0300 |
---|---|---|
committer | Catalin Marinas <catalin.marinas@arm.com> | 2021-05-14 19:11:16 +0300 |
commit | 588a513d34257fdde95a9f0df0202e31998e85c6 (patch) | |
tree | 053e87f91afc329f6a187eae1a2e29ecaf6a3eed | |
parent | af44068c581c028fd9897ca75a10fa310d8fc449 (diff) | |
download | linux-588a513d34257fdde95a9f0df0202e31998e85c6.tar.xz |
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.c | 4 |
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); |