On Thu, 23 May 2013 14:25:48 +0900 HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> wrote:
> This patch introduces mmap_vmcore().
>
> Don't permit writable nor executable mapping even with mprotect()
> because this mmap() is aimed at reading crash dump memory.
> Non-writable mapping is also requirement of remap_pfn_range() when
> mapping linear pages on non-consecutive physical pages; see
> is_cow_mapping().
>
> Set VM_MIXEDMAP flag to remap memory by remap_pfn_range and by
> remap_vmalloc_range_pertial at the same time for a single
> vma. do_munmap() can correctly clean partially remapped vma with two
> functions in abnormal case. See zap_pte_range(), vm_normal_page() and
> their comments for details.
>
> On x86-32 PAE kernels, mmap() supports at most 16TB memory only. This
> limitation comes from the fact that the third argument of
> remap_pfn_range(), pfn, is of 32-bit length on x86-32: unsigned long.
More reviewing and testing, please.
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: vmcore-support-mmap-on-proc-vmcore-fix
use min(), switch to conventional error-unwinding approach
Cc: Atsushi Kumagai <kumagai-atsushi at mxc.nes.nec.co.jp>
Cc: HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro at jp.fujitsu.com>
Cc: Lisa Mitchell <lisa.mitchell at hp.com>
Cc: Vivek Goyal <vgoyal at redhat.com>
Cc: Zhang Yanfei <zhangyanfei at cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---
fs/proc/vmcore.c | 27 ++++++++++-----------------
1 file changed, 10 insertions(+), 17 deletions(-)
diff -puN fs/proc/vmcore.c~vmcore-support-mmap-on-proc-vmcore-fix fs/proc/vmcore.c
--- a/fs/proc/vmcore.c~vmcore-support-mmap-on-proc-vmcore-fix
+++ a/fs/proc/vmcore.c
@@ -218,9 +218,7 @@ static int mmap_vmcore(struct file *file
if (start < elfcorebuf_sz) {
u64 pfn;
- tsz = elfcorebuf_sz - start;
- if (size < tsz)
- tsz = size;
+ tsz = min(elfcorebuf_sz - (size_t)start, size);
pfn = __pa(elfcorebuf + start) >> PAGE_SHIFT;
if (remap_pfn_range(vma, vma->vm_start, pfn, tsz,
vma->vm_page_prot))
@@ -236,15 +234,11 @@ static int mmap_vmcore(struct file *file
if (start < elfcorebuf_sz + elfnotes_sz) {
void *kaddr;
- tsz = elfcorebuf_sz + elfnotes_sz - start;
- if (size < tsz)
- tsz = size;
+ tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)start, size);
kaddr = elfnotes_buf + start - elfcorebuf_sz;
if (remap_vmalloc_range_partial(vma, vma->vm_start + len,
- kaddr, tsz)) {
- do_munmap(vma->vm_mm, vma->vm_start, len);
- return -EAGAIN;
- }
+ kaddr, tsz))
+ goto fail;
size -= tsz;
start += tsz;
len += tsz;
@@ -257,16 +251,12 @@ static int mmap_vmcore(struct file *file
if (start < m->offset + m->size) {
u64 paddr = 0;
- tsz = m->offset + m->size - start;
- if (size < tsz)
- tsz = size;
+ tsz = min_t(size_t, m->offset + m->size - start, size);
paddr = m->paddr + start - m->offset;
if (remap_pfn_range(vma, vma->vm_start + len,
paddr >> PAGE_SHIFT, tsz,
- vma->vm_page_prot)) {
- do_munmap(vma->vm_mm, vma->vm_start, len);
- return -EAGAIN;
- }
+ vma->vm_page_prot))
+ goto fail;
size -= tsz;
start += tsz;
len += tsz;
@@ -277,6 +267,9 @@ static int mmap_vmcore(struct file *file
}
return 0;
+fail:
+ do_munmap(vma->vm_mm, vma->vm_start, len);
+ return -EAGAIN;
}
static const struct file_operations proc_vmcore_operations = {
_
