[PATCH 2/2] [PATCH 2/2] proc-vmcore: wrong data type casting fix

[dyoung]

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 min_lt instead so that the variables are not truncated.

Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
Signed-off-by: Dave Young <dyoung@xxxxxxxxxx>
---
 fs/proc/vmcore.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- linux.orig/fs/proc/vmcore.c
+++ linux/fs/proc/vmcore.c
@@ -231,7 +231,8 @@ 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_lt(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 +462,7 @@ 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_lt(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,