libusb: LIBUSB_DEBUG environment variable override of libusb_set_debug

The debug level generally just controls verbosity of libusb for debugging
libusb devices/usage. We allow the environment to set the debug level
independent of the application, but the application will always override
this if it explicitly sets the debug level.

Changing the environment is easy, but patching the software to change the
debug level isn't necessarily easy or possible. Further, there's this
write-only debug_fixed variable that would seem to imply that the debug
level should be fixed, but it isn't currently used. Change the logic to use
strtol() so we can detect real 0 vs. conversion failure, then honor
debug_fixed in libusb_set_debug.

Reviewed by:	hselasky
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D21877

1 files changed, 19 insertions, 4 deletions

diff --git a/lib/libusb/libusb10.c b/lib/libusb/libusb10.c
index 43199c089e7c..6f61353a76b3 100644
--- a/lib/libusb/libusb10.c
+++ b/lib/libusb/libusb10.c
@@ -91,7 +91,8 @@ void
 libusb_set_debug(libusb_context *ctx, int level)
 {
 	ctx = GET_CONTEXT(ctx);
-	if (ctx)
+	/* debug_fixed is set when the environment overrides libusb_set_debug */
+	if (ctx && ctx->debug_fixed == 0)
 		ctx->debug = level;
 }
 
@@ -132,7 +133,7 @@ libusb_init(libusb_context **context)
 {
 	struct libusb_context *ctx;
 	pthread_condattr_t attr;
-	char *debug;
+	char *debug, *ep;
 	int ret;
 
 	ctx = malloc(sizeof(*ctx));
@@ -143,9 +144,23 @@ libusb_init(libusb_context **context)
 
 	debug = getenv("LIBUSB_DEBUG");
 	if (debug != NULL) {
-		ctx->debug = atoi(debug);
-		if (ctx->debug != 0)
+		/*
+		 * If LIBUSB_DEBUG is set, we'll honor that and use it to
+		 * override libusb_set_debug calls.
+		 */
+		errno = 0;
+		ctx->debug = strtol(debug, &ep, 10);
+		if (errno == 0 && *ep == '\0') {
 			ctx->debug_fixed = 1;
+		} else {
+			/*
+			 * LIBUSB_DEBUG conversion failed for some reason, but
+			 * we don't care about the specifics all that much.  We
+			 * can't use it either way.  Force it to the default,
+			 * 0, in case we had a partial number.
+			 */
+			ctx->debug = 0;
+		}
 	}
 	TAILQ_INIT(&ctx->pollfds);
 	TAILQ_INIT(&ctx->tr_done);