Commit 72ed7de7 authored by Jiri Slaby's avatar Jiri Slaby Committed by Ingo Molnar

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: default avatarJiri 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: default avatarIngo Molnar <mingo@elte.hu>
parent ae1b22f6
...@@ -16,6 +16,22 @@ static void *kdump_buf_page; ...@@ -16,6 +16,22 @@ static void *kdump_buf_page;
/* Stores the physical address of elf header of crash image. */ /* Stores the physical address of elf header of crash image. */
unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX; 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" * copy_oldmem_page - copy one page from "oldmem"
* @pfn: page frame number to be copied * @pfn: page frame number to be copied
...@@ -41,6 +57,9 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, ...@@ -41,6 +57,9 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
if (!csize) if (!csize)
return 0; return 0;
if (!is_crashed_pfn_valid(pfn))
return -EFAULT;
vaddr = kmap_atomic_pfn(pfn, KM_PTE0); vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
if (!userbuf) { if (!userbuf) {
......
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