Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

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

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

arch/x86/kernel/crash_dump_32.c

+19 −0
Original line number Diff line number Diff line
@@ -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) {