Messages in this thread Patch in this message | | | From | Yaohui Wang <> | Subject | [PATCH] mm: fix pfn calculation mistake in __ioremap_check_ram | Date | Mon, 7 Jun 2021 17:19:39 +0800 |
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According to the source code in function arch/x86/mm/ioremap.c:__ioremap_caller, after __ioremap_check_mem, if the mem range is IORES_MAP_SYSTEM_RAM, then __ioremap_caller should fail. But because of the pfn calculation problem, __ioremap_caller can success on IORES_MAP_SYSTEM_RAM region when the @size parameter is less than PAGE_SIZE. This may cause misuse of the ioremap function and raise the risk of performance issues. For example, ioremap(phys, PAGE_SIZE-1) may cause the direct memory mapping of @phys to be uncached, and iounmap won't revert this change. This patch fixes this issue.
In arch/x86/mm/ioremap.c:__ioremap_check_ram, start_pfn should wrap down the res->start address, and end_pfn should wrap up the res->end address. This makes the check more strict and should be more reasonable.
Signed-off-by: Ben Luo <luoben@linux.alibaba.com> Signed-off-by: Yahui Wang <yaohuiwang@linux.alibaba.com> --- arch/x86/mm/ioremap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c index 9e5ccc56f..79adf0d2d 100644 --- a/arch/x86/mm/ioremap.c +++ b/arch/x86/mm/ioremap.c @@ -74,8 +74,8 @@ static unsigned int __ioremap_check_ram(struct resource *res) if ((res->flags & IORESOURCE_SYSTEM_RAM) != IORESOURCE_SYSTEM_RAM) return 0; - start_pfn = (res->start + PAGE_SIZE - 1) >> PAGE_SHIFT; - stop_pfn = (res->end + 1) >> PAGE_SHIFT; + start_pfn = res->start >> PAGE_SHIFT; + stop_pfn = (res->end + PAGE_SIZE) >> PAGE_SHIFT; if (stop_pfn > start_pfn) { for (i = 0; i < (stop_pfn - start_pfn); ++i) if (pfn_valid(start_pfn + i) && -- 2.25.1
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