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

PATCH New Kees Cook 1 participant 1 message Mar 27, 2018 Char and misc drivers

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Kees Cook

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PATCH 1/1 /dev/mem: Avoid overwriting "err" in read_mem()

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

Reported-by Brad Spengler <[email protected]>
Fixes 22ec1a2aea73 ("/dev/mem: Add bounce buffer for copy-out")
Cc [email protected]
Signed-off-by Kees Cook <[email protected]>
---
 drivers/char/mem.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
drivers/char/mem.c +3 -3
index 052011bcf100..ffeb60d3434c 100644
@@ -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);
Signature · 6 lines
2.7.4


-- 
Kees Cook
Pixel Security