uml: check length in exitcode_proc_write()

201f99f1 · Dan Carpenter <[email protected]> · 2013-10-29 22:06:04 +03:00

We don't cap the size of buffer from the user so we could write past the
end of the array here.  Only root can write to this file.

Reported-by: Nico Golde <[email protected]>
Reported-by: Fabian Yamaguchi <[email protected]>
Signed-off-by: Dan Carpenter <[email protected]>
Cc: [email protected]
Signed-off-by: Linus Torvalds <[email protected]>

Commit: 201f99f170df14ba52ea4c52847779042b7a623b
Parents: 7314e613

Changes

1 files changed · +3 −1

File	Status	Add	Del	Content
arch/um/kernel/exitcode.c	modified	+3	−1	View file

arch/um/kernel/exitcode.c

View file

diff --git a/arch/um/kernel/exitcode.c b/arch/um/kernel/exitcode.c
index 829df49..41ebbfe 100644
--- a/arch/um/kernel/exitcode.c
+++ b/arch/um/kernel/exitcode.c
@@ -40,9 +40,11 @@ static ssize_t exitcode_proc_write(struct file *file,
 		const char __user *buffer, size_t count, loff_t *pos)
 {
 	char *end, buf[sizeof("nnnnn\0")];
+	size_t size;
 	int tmp;
 
-	if (copy_from_user(buf, buffer, count))
+	size = min(count, sizeof(buf));
+	if (copy_from_user(buf, buffer, size))
 		return -EFAULT;
 
 	tmp = simple_strtol(buf, &end, 0);