Commit-ID: 72ed7de74e8f0fad0d8e567ae1f987b740accb3f
Gitweb: http://git.kernel.org/tip/72ed7de74e8f0fad0d8e567ae1f987b740accb3f
Author: Jiri Slaby <jirislaby@xxxxxxxxx>
AuthorDate: Mon, 26 Oct 2009 11:11:43 +0100
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Mon, 26 Oct 2009 12:38:59 +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@xxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Simon Horman <horms@xxxxxxxxxxxx>
Cc: Paul Mundt <lethal@xxxxxxxxxxxx>
LKML-Reference: <1256551903-30567-1-git-send-email-jirislaby@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
arch/x86/kernel/crash_dump_32.c | 19 +++++++++++++++++++
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 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) {
--
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