2021-05-12 13:34:09

by Marcelo Henrique Cerri

[permalink] [raw]
Subject: [PATCH] proc: Avoid mixing integer types in mem_rw()

Use size_t when capping the count argument received by mem_rw(). Since
count is size_t, using min_t(int, ...) can lead to a negative value
that will later be passed to access_remote_vm(), which can cause
unexpected behavior.

Since we are capping the value to at maximum PAGE_SIZE, the conversion
from size_t to int when passing it to access_remote_vm() as "len"
shouldn't be a problem.

Reviewed-by: David Disseldorp <[email protected]>
Signed-off-by: Thadeu Lima de Souza Cascardo <[email protected]>
Signed-off-by: Marcelo Henrique Cerri <[email protected]>
---
fs/proc/base.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 3851bfcdba56..8dbc6a1aaadb 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -854,7 +854,7 @@ static ssize_t mem_rw(struct file *file, char __user *buf,
flags = FOLL_FORCE | (write ? FOLL_WRITE : 0);

while (count > 0) {
- int this_len = min_t(int, count, PAGE_SIZE);
+ size_t this_len = min_t(size_t, count, PAGE_SIZE);

if (write && copy_from_user(page, buf, this_len)) {
copied = -EFAULT;
--
2.25.1