proc-vmcore: wrong data type casting fix

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 <[email protected]>
Signed-off-by: Dave Young <[email protected]>
Cc: HATAYAMA Daisuke <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: Jianyu Zhan <[email protected]>
Cc: Minfei Huang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions