From: Gerhard Sittig <redacted>
Date: Fri, 9 Feb 2018 18:05:38 +0000 (+0100)
Subject: hp-3457a: fix potential NULL dereference
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=1674225a2fa7e1b6d0c235549e1a7f6ec44e7520;p=libsigrok.git

hp-3457a: fix potential NULL dereference

Check the active channels' list for not being empty, before
dereferencing pointers.

This was reported by clang's scan-build.
---

diff --git a/src/hardware/hp-3457a/api.c b/src/hardware/hp-3457a/api.c
index 5325224e..64fdab54 100644
--- a/src/hardware/hp-3457a/api.c
+++ b/src/hardware/hp-3457a/api.c
@@ -359,8 +359,13 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi)
 		return SR_ERR_ARG;
 	}
 
-	devc->current_channel = devc->active_channels->data;
 	devc->num_active_channels = g_slist_length(devc->active_channels);
+	if (!devc->num_active_channels) {
+		sr_err("Need at least one active channel!");
+		g_slist_free(devc->active_channels);
+		return SR_ERR_ARG;
+	}
+	devc->current_channel = devc->active_channels->data;
 
 	hp_3457a_select_input(sdi, front_selected ? CONN_FRONT : CONN_REAR);