2016-03-11 08:15:27

by Dave Young

Subject: [PATCH] proc-vmcore: wrong data type casting fix

On i686 PAE enabled machine the contiguous physical area could be large
and it can cause triming down variables in below calculation in
read_vmcore() and mmap_vmcore():

tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);

Then the real size passed down is not correct any more.
Suppose m->offset + m->size - *fpos being truncated to 0, buflen >0 then
we will get tsz = 0. It is of course not an expected result.

During out test there are two problems caused by it:
1) read_vmcore will refuse to continue so makedumpfile fails.
2) mmap_vmcore will trigger BUG_ON() in remap_pfn_range().

Use unsigned long long in min_t instead so that the variables are not
truncated.

Signed-off-by: Baoquan He <[email protected]>
Signed-off-by: Dave Young <[email protected]>
---
fs/proc/vmcore.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- linux-x86.orig/fs/proc/vmcore.c
+++ linux-x86/fs/proc/vmcore.c
@@ -231,7 +231,9 @@ static ssize_t __read_vmcore(char *buffe

list_for_each_entry(m, &vmcore_list, list) {
if (*fpos < m->offset + m->size) {
- tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
+ tsz = (size_t)min_t(unsigned long long,
+ m->offset + m->size - *fpos,
+ buflen);
start = m->paddr + *fpos - m->offset;
tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
if (tmp < 0)
@@ -461,7 +463,8 @@ static int mmap_vmcore(struct file *file
if (start < m->offset + m->size) {
u64 paddr = 0;

- tsz = min_t(size_t, m->offset + m->size - start, size);
+ tsz = (size_t)min_t(unsigned long long,
+ m->offset + m->size - start, size);
paddr = m->paddr + start - m->offset;
if (vmcore_remap_oldmem_pfn(vma, vma->vm_start + len,
paddr >> PAGE_SHIFT, tsz,

2016-03-11 08:31:50

by Baoquan He

Subject: Re: [PATCH] proc-vmcore: wrong data type casting fix

On 03/11/16 at 04:15pm, Dave Young wrote:
> On i686 PAE enabled machine the contiguous physical area could be large
> and it can cause triming down variables in below calculation in
> read_vmcore() and mmap_vmcore():
>
> tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
>
> Then the real size passed down is not correct any more.
> Suppose m->offset + m->size - *fpos being truncated to 0, buflen >0 then
> we will get tsz = 0. It is of course not an expected result.
>
> During out test there are two problems caused by it:
~ our
> 1) read_vmcore will refuse to continue so makedumpfile fails.
> 2) mmap_vmcore will trigger BUG_ON() in remap_pfn_range().
>
> Use unsigned long long in min_t instead so that the variables are not
> truncated.
>
> Signed-off-by: Baoquan He <[email protected]>
> Signed-off-by: Dave Young <[email protected]>
> ---
> fs/proc/vmcore.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> --- linux-x86.orig/fs/proc/vmcore.c
> +++ linux-x86/fs/proc/vmcore.c
> @@ -231,7 +231,9 @@ static ssize_t __read_vmcore(char *buffe
>
> list_for_each_entry(m, &vmcore_list, list) {
> if (*fpos < m->offset + m->size) {
> - tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
> + tsz = (size_t)min_t(unsigned long long,
> + m->offset + m->size - *fpos,
> + buflen);
> start = m->paddr + *fpos - m->offset;
> tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
> if (tmp < 0)
> @@ -461,7 +463,8 @@ static int mmap_vmcore(struct file *file
> if (start < m->offset + m->size) {
> u64 paddr = 0;
>
> - tsz = min_t(size_t, m->offset + m->size - start, size);
> + tsz = (size_t)min_t(unsigned long long,
> + m->offset + m->size - start, size);
> paddr = m->paddr + start - m->offset;
> if (vmcore_remap_oldmem_pfn(vma, vma->vm_start + len,
> paddr >> PAGE_SHIFT, tsz,