76 lines
2.9 KiB
Diff
76 lines
2.9 KiB
Diff
From: Paul Burton <paul.burton@mips.com>
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Date: Tue, 28 May 2019 17:05:03 +0000
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Subject: MIPS: Bounds check virt_addr_valid
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Origin: https://git.kernel.org/linus/074a1e1167afd82c26f6d03a9a8b997d564bb241
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The virt_addr_valid() function is meant to return true iff
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virt_to_page() will return a valid struct page reference. This is true
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iff the address provided is found within the unmapped address range
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between PAGE_OFFSET & MAP_BASE, but we don't currently check for that
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condition. Instead we simply mask the address to obtain what will be a
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physical address if the virtual address is indeed in the desired range,
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shift it to form a PFN & then call pfn_valid(). This can incorrectly
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return true if called with a virtual address which, after masking,
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happens to form a physical address corresponding to a valid PFN.
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For example we may vmalloc an address in the kernel mapped region
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starting a MAP_BASE & obtain the virtual address:
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addr = 0xc000000000002000
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When masked by virt_to_phys(), which uses __pa() & in turn CPHYSADDR(),
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we obtain the following (bogus) physical address:
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addr = 0x2000
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In a common system with PHYS_OFFSET=0 this will correspond to a valid
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struct page which should really be accessed by virtual address
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PAGE_OFFSET+0x2000, causing virt_addr_valid() to incorrectly return 1
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indicating that the original address corresponds to a struct page.
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This is equivalent to the ARM64 change made in commit ca219452c6b8
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("arm64: Correctly bounds check virt_addr_valid").
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This fixes fallout when hardened usercopy is enabled caused by the
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related commit 517e1fbeb65f ("mm/usercopy: Drop extra
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is_vmalloc_or_module() check") which removed a check for the vmalloc
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range that was present from the introduction of the hardened usercopy
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feature.
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Signed-off-by: Paul Burton <paul.burton@mips.com>
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References: ca219452c6b8 ("arm64: Correctly bounds check virt_addr_valid")
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References: 517e1fbeb65f ("mm/usercopy: Drop extra is_vmalloc_or_module() check")
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Reported-by: Julien Cristau <jcristau@debian.org>
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Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
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Tested-by: YunQiang Su <ysu@wavecomp.com>
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URL: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=929366
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Cc: stable@vger.kernel.org # v4.12+
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Cc: linux-mips@vger.kernel.org
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Cc: Yunqiang Su <ysu@wavecomp.com>
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---
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arch/mips/mm/mmap.c | 5 +++++
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1 file changed, 5 insertions(+)
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diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
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index 2f616ebeb7e0..7755a1fad05a 100644
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--- a/arch/mips/mm/mmap.c
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+++ b/arch/mips/mm/mmap.c
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@@ -203,6 +203,11 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
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int __virt_addr_valid(const volatile void *kaddr)
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{
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+ unsigned long vaddr = (unsigned long)vaddr;
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+
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+ if ((vaddr < PAGE_OFFSET) || (vaddr >= MAP_BASE))
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+ return 0;
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+
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return pfn_valid(PFN_DOWN(virt_to_phys(kaddr)));
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}
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EXPORT_SYMBOL_GPL(__virt_addr_valid);
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--
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2.20.1
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