linux-kernel - Re: [PATCH] usbip: fix usbip bind writing random string after command in match

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Date:   Thu, 14 Dec 2017 11:23:39 +0100 (CET)
From:   Juan Zea <juan.zea@...del.com>
To:     shuah@...nel.org
Cc:     linux-usb@...r.kernel.org,
        Valentina Manea <valentina.manea.m@...il.com>,
        linux-kernel@...r.kernel.org, Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH] usbip: fix usbip bind writing random string after
 command in match_busid

> Why not use the return value from snprintf() for length, instead of calling
strlen(command)?

Yes, that makes sense. Something like this?

diff --git a/tools/usb/usbip/src/utils.c b/tools/usb/usbip/src/utils.c
index 2b3d6d2..3d7b42e 100644
--- a/tools/usb/usbip/src/utils.c
+++ b/tools/usb/usbip/src/utils.c
@@ -30,6 +30,7 @@ int modify_match_busid(char *busid, int add)
        char command[SYSFS_BUS_ID_SIZE + 4];
        char match_busid_attr_path[SYSFS_PATH_MAX];
        int rc;
+       int cmd_size;
 
        snprintf(match_busid_attr_path, sizeof(match_busid_attr_path),
                 "%s/%s/%s/%s/%s/%s", SYSFS_MNT_PATH, SYSFS_BUS_NAME,
@@ -37,12 +38,14 @@ int modify_match_busid(char *busid, int add)
                 attr_name);
 
        if (add)
-               snprintf(command, SYSFS_BUS_ID_SIZE + 4, "add %s", busid);
+               cmd_size = snprintf(command, SYSFS_BUS_ID_SIZE + 4, "add %s",
+                                   busid);
        else
-               snprintf(command, SYSFS_BUS_ID_SIZE + 4, "del %s", busid);
+               cmd_size = snprintf(command, SYSFS_BUS_ID_SIZE + 4, "del %s",
+                                   busid);
 
        rc = write_sysfs_attribute(match_busid_attr_path, command,
-                                  sizeof(command));
+                                  cmd_size);
        if (rc < 0) {
                dbg("failed to write match_busid: %s", strerror(errno));
                return -1;


Regards,
Juan