* FAILED: patch "[PATCH] arm64: mm: check for upper PAGE_SHIFT bits in pfn_valid()" failed to apply to 3.18-stable tree
@ 2018-08-30 16:56 gregkh
0 siblings, 0 replies; only message in thread
From: gregkh @ 2018-08-30 16:56 UTC (permalink / raw)
To: ghackmann, ghackmann, will.deacon; +Cc: stable
The patch below does not apply to the 3.18-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>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 5ad356eabc47d26a92140a0c4b20eba471c10de3 Mon Sep 17 00:00:00 2001
From: Greg Hackmann <ghackmann@android.com>
Date: Wed, 15 Aug 2018 12:51:21 -0700
Subject: [PATCH] arm64: mm: check for upper PAGE_SHIFT bits in pfn_valid()
ARM64's pfn_valid() shifts away the upper PAGE_SHIFT bits of the input
before seeing if the PFN is valid. This leads to false positives when
some of the upper bits are set, but the lower bits match a valid PFN.
For example, the following userspace code looks up a bogus entry in
/proc/kpageflags:
int pagemap = open("/proc/self/pagemap", O_RDONLY);
int pageflags = open("/proc/kpageflags", O_RDONLY);
uint64_t pfn, val;
lseek64(pagemap, [...], SEEK_SET);
read(pagemap, &pfn, sizeof(pfn));
if (pfn & (1UL << 63)) { /* valid PFN */
pfn &= ((1UL << 55) - 1); /* clear flag bits */
pfn |= (1UL << 55);
lseek64(pageflags, pfn * sizeof(uint64_t), SEEK_SET);
read(pageflags, &val, sizeof(val));
}
On ARM64 this causes the userspace process to crash with SIGSEGV rather
than reading (1 << KPF_NOPAGE). kpageflags_read() treats the offset as
valid, and stable_page_flags() will try to access an address between the
user and kernel address ranges.
Fixes: c1cc1552616d ("arm64: MMU initialisation")
Cc: stable@vger.kernel.org
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 325cfb3b858a..811f9f8b3bb0 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -287,7 +287,11 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
int pfn_valid(unsigned long pfn)
{
- return memblock_is_map_memory(pfn << PAGE_SHIFT);
+ phys_addr_t addr = pfn << PAGE_SHIFT;
+
+ if ((addr >> PAGE_SHIFT) != pfn)
+ return 0;
+ return memblock_is_map_memory(addr);
}
EXPORT_SYMBOL(pfn_valid);
#endif
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2018-08-30 16:56 FAILED: patch "[PATCH] arm64: mm: check for upper PAGE_SHIFT bits in pfn_valid()" failed to apply to 3.18-stable tree gregkh
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