The following commit has been merged in the linux branch: commit 72ed7de74e8f0fad0d8e567ae1f987b740accb3f Author: Jiri Slaby jirislaby@gmail.com Date: Mon Oct 26 11:11:43 2009 +0100

x86: crash_dump: Fix non-pae kdump kernel memory accesses

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.

[v2] - fix comments - move ifdefs inside the function

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 LKML-Reference: 1256551903-30567-1-git-send-email-jirislaby@gmail.com Signed-off-by: Ingo Molnar mingo@elte.hu

diff --git a/arch/x86/kernel/crash_dump_32.c b/arch/x86/kernel/crash_dump_32.c index f7cdb3b..cd97ce1 100644 --- a/arch/x86/kernel/crash_dump_32.c +++ b/arch/x86/kernel/crash_dump_32.c @@ -16,6 +16,22 @@ static void *kdump_buf_page; /* Stores the physical address of elf header of crash image. */ unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;

+static inline bool is_crashed_pfn_valid(unsigned long pfn) +{ +#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. pte must fit into unsigned long. In fact the + * test checks high 12 bits for being zero (pfn will be shifted left + * by PAGE_SHIFT). + */ + return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn; +#else + return true; +#endif +} + /** * copy_oldmem_page - copy one page from "oldmem" * @pfn: page frame number to be copied @@ -41,6 +57,9 @@ 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) {