On i686 PAE enabled machine the contiguous physical area could be large
and it can cause trimming down variables in below calculation in
read_vmcore() and mmap_vmcore():
tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
That is, the types being used is like below on i686:
m->offset: unsigned long long int
m->size: unsigned long long int
*fpos: loff_t (long long int)
buflen: size_t (unsigned int)
So casting (m->offset + m->size - *fpos) by size_t means truncating a given
value by 4GB.
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. Similarly we
could also get other truncated values less than buflen. Then the real size
passed down is not correct any more.
If (m->offset + m->size - *fpos) is above 4GB, read_vmcore or mmap_vmcore
use the min_t result with truncated values being compared to buflen.
Then, fpos proceeds with the wrong value so that we reach below bugs:
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 in are not
truncated.
Signed-off-by: Baoquan He <bhe at redhat.com>
Signed-off-by: Dave Young <dyoung at redhat.com>
---
v2->v3: tweak patch description about bug details for people to get the
problem easier.
v1->v2: spelling fix in patch log
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,
