ath9k: dfs_debug fix possible NULL dereference

Fix possible NULL (sc->dfs_detector) pointer dereference.

Detected by Smatch:
drivers/net/wireless/ath/ath9k/dfs_debug.c:67 read_file_dfs()
error: we previously assumed 'sc->dfs_detector' could be null (see line 47)

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/ath/ath9k/dfs_debug.c b/drivers/net/wireless/ath/ath9k/dfs_debug.c
index 90b8342d1ed4bd2e95389541f299d49d59261e6a..8824610c21fb3a3476a281f6b3435213ebef12cd 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/dfs_debug.c
+++ b/drivers/net/wireless/ath/ath9k/dfs_debug.c
@@ -44,14 +44,20 @@ static ssize_t read_file_dfs(struct file *file, char __user *user_buf,
        if (buf == NULL)
                return -ENOMEM;
 
-       if (sc->dfs_detector)
-               dfs_pool_stats = sc->dfs_detector->get_stats(sc->dfs_detector);
-
        len += scnprintf(buf + len, size - len, "DFS support for "
                         "macVersion = 0x%x, macRev = 0x%x: %s\n",
                         hw_ver->macVersion, hw_ver->macRev,
                         (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_DFS) ?
                                        "enabled" : "disabled");
+
+       if (!sc->dfs_detector) {
+               len += scnprintf(buf + len, size - len,
+                                "DFS detector not enabled\n");
+               goto exit;
+       }
+
+       dfs_pool_stats = sc->dfs_detector->get_stats(sc->dfs_detector);
+
        len += scnprintf(buf + len, size - len, "Pulse detector statistics:\n");
        ATH9K_DFS_STAT("pulse events reported   ", pulses_total);
        ATH9K_DFS_STAT("invalid pulse events    ", pulses_no_dfs);
@@ -76,6 +82,7 @@ static ssize_t read_file_dfs(struct file *file, char __user *user_buf,
        ATH9K_DFS_POOL_STAT("Seqs. alloc error       ", pseq_alloc_error);
        ATH9K_DFS_POOL_STAT("Seqs. in use            ", pseq_used);
 
+exit:
        if (len > size)
                len = size;