ath9k: Fix write callback of 'debug' which configures debug mask

Handle error condition on copy_from_user() properly and
make sure a NUL terminated char[] is sent to strict_strtoul()
for proper conversion.

Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 14 insertions, 8 deletions

diff --git a/drivers/net/wireless/ath/ath9k/debug.c b/drivers/net/wireless/ath/ath9k/debug.c
index a42d631e7456..6d20725d6451 100644
--- a/drivers/net/wireless/ath/ath9k/debug.c
+++ b/drivers/net/wireless/ath/ath9k/debug.c
@@ -49,8 +49,9 @@ static ssize_t read_file_debug(struct file *file, char __user *user_buf,
 {
         struct ath_softc *sc = file->private_data;
         char buf[32];
-        unsigned int len = 0;
-        len += snprintf(buf, sizeof(buf), "0x%08x\n", sc->debug.debug_mask);
+        unsigned int len;
+
+        len = snprintf(buf, sizeof(buf), "0x%08x\n", sc->debug.debug_mask);
         return simple_read_from_buffer(user_buf, count, ppos, buf, len);
 }
 
@@ -60,12 +61,17 @@ static ssize_t write_file_debug(struct file *file, const char __user *user_buf,
         struct ath_softc *sc = file->private_data;
         unsigned long mask;
         char buf[32];
-        if (copy_from_user(buf, user_buf, (sizeof(buf) - 1) < count ?
-                (sizeof(buf) - 1) : count))
-                return 0;
-        buf[sizeof(buf)-1] = 0;
-        if (strict_strtoul(buf, 0, &mask) == 0)
-                sc->debug.debug_mask = mask;
+        ssize_t len;
+
+        len = min(count, sizeof(buf) - 1);
+        if (copy_from_user(buf, user_buf, len))
+                return -EINVAL;
+
+        buf[len] = '\0';
+        if (strict_strtoul(buf, 0, &mask))
+                return -EINVAL;
+
+        sc->debug.debug_mask = mask;
         return count;
 }