From: Kees Cook <keescook@chromium.org>
Date: Tue, 27 Mar 2018 21:06:14 +0000 (-0700)
Subject: /dev/mem: Avoid overwriting "err" in read_mem()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=5f834dd24baec1f9926e8a06609e0906fd607b06;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

/dev/mem: Avoid overwriting "err" in read_mem()

commit b5b38200ebe54879a7264cb6f33821f61c586a7e upstream.

Successes in probe_kernel_read() would mask failures in copy_to_user()
during read_mem().

Reported-by: Brad Spengler <spender@grsecurity.net>
Fixes: 22ec1a2aea73 ("/dev/mem: Add bounce buffer for copy-out")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 3a70dba2c645..f11224a5dc5c 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -137,7 +137,7 @@ static ssize_t read_mem(struct file *file, char __user *buf,
 
 	while (count > 0) {
 		unsigned long remaining;
-		int allowed;
+		int allowed, probe;
 
 		sz = size_inside_page(p, count);
 
@@ -160,9 +160,9 @@ static ssize_t read_mem(struct file *file, char __user *buf,
 			if (!ptr)
 				goto failed;
 
-			err = probe_kernel_read(bounce, ptr, sz);
+			probe = probe_kernel_read(bounce, ptr, sz);
 			unxlate_dev_mem_ptr(p, ptr);
-			if (err)
+			if (probe)
 				goto failed;
 
 			remaining = copy_to_user(buf, bounce, sz);