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authorJiri Slaby <jirislaby@gmail.com>2009-10-26 11:11:43 +0100
committerIngo Molnar <mingo@elte.hu>2009-10-26 12:38:59 +0100
commit72ed7de74e8f0fad0d8e567ae1f987b740accb3f (patch)
treedd8e7dbd4b6305bcca35fc2cfe29479918e034d2 /arch/x86/kernel/crash_dump_32.c
parentae1b22f6e46c03cede7cea234d0bf2253b4261cf (diff)
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>
Diffstat (limited to 'arch/x86/kernel/crash_dump_32.c')
-rw-r--r--arch/x86/kernel/crash_dump_32.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/arch/x86/kernel/crash_dump_32.c b/arch/x86/kernel/crash_dump_32.c
index f7cdb3b457a..cd97ce18c29 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) {