[PATCH] proc/vmcore: fix signedness bug in read_from_oldmem()

[Dan Carpenter <dan.carpenter@linaro.org>]

The bug is the error handling:

	if (tmp < nr_bytes) {

"tmp" can hold negative error codes but because "nr_bytes" is type
size_t the negative error codes are treated as very high positive
values (success).  Fix this by changing "nr_bytes" to type ssize_t.  The
"nr_bytes" variable is used to store values between 1 and PAGE_SIZE and
they can fit in ssize_t without any issue.

Fixes: 5d8de293c224 ("vmcore: convert copy_oldmem_page() to take an iov_iter")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
 fs/proc/vmcore.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index cb80a7703d58..1fb213f379a5 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -132,7 +132,7 @@ ssize_t read_from_oldmem(struct iov_iter *iter, size_t count,
 			 u64 *ppos, bool encrypted)
 {
 	unsigned long pfn, offset;
-	size_t nr_bytes;
+	ssize_t nr_bytes;
 	ssize_t read = 0, tmp;
 	int idx;
 
-- 
2.39.2