Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH 1/1] crash_dump: fix non-pae kdump kernel memory accesses | Date | Fri, 23 Oct 2009 17:45:29 +0200 |
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Non-PAE 32-bit dump kernels may wrap an address around 4G and poke unwanted space. ptes there are 32-bit long, and since pfn << PAGE_SIZE may exceed this limit, high pfn bits are cropped and wrong address mapped by kmap_atomic_pfn in copy_oldmem_page.
Don't allow this behavior in non-PAE kdump kernels by checking pfns passed into copy_oldmem_page. In the case of failure, userspace process gets EFAULT.
Signed-off-by: Jiri Slaby <jirislaby@gmail.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Simon Horman <horms@verge.net.au> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Ingo Molnar <mingo@elte.hu> --- arch/x86/kernel/crash_dump_32.c | 16 ++++++++++++++++ 1 files changed, 16 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/crash_dump_32.c b/arch/x86/kernel/crash_dump_32.c index f7cdb3b..b78dab8 100644 --- a/arch/x86/kernel/crash_dump_32.c +++ b/arch/x86/kernel/crash_dump_32.c @@ -16,6 +16,19 @@ static void *kdump_buf_page; /* Stores the physical address of elf header of crash image. */ unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX; +#ifndef CONFIG_X86_PAE +/* non-PAE kdump kernel executed from a PAE one will crop high pte bits and + poke unwanted space counting again from address 0, we don't want that */ +static inline bool is_crashed_pfn_valid(unsigned long pfn) +{ + /* on non-PAE pte must fit into unsigned long + in fact the test is (pfn & 0x000fffff) */ + return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn; +} +#else +static inline bool is_crashed_pfn_valid(unsigned long pfn) { return true; } +#endif + /** * copy_oldmem_page - copy one page from "oldmem" * @pfn: page frame number to be copied @@ -41,6 +54,9 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, if (!csize) return 0; + if (!is_crashed_pfn_valid(pfn)) + return -EFAULT; + vaddr = kmap_atomic_pfn(pfn, KM_PTE0); if (!userbuf) { -- 1.6.4.2
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