libertas: potential oops in debugfs

commit a497e47d4aec37aaf8f13509f3ef3d1f6a717d88 upstream.

If we do a zero size allocation then it will oops.  Also we can't be
sure the user passes us a NUL terminated string so I've added a
terminator.

This code can only be triggered by root.

Reported-by: Nico Golde <nico@ngolde.de>
Reported-by: Fabian Yamaguchi <fabs@goesec.de>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/net/wireless/libertas/debugfs.c b/drivers/net/wireless/libertas/debugfs.c
index d8d8f0d..35d86fa 100644 (file)
--- a/drivers/net/wireless/libertas/debugfs.c
+++ b/drivers/net/wireless/libertas/debugfs.c
@@ -919,7 +919,10 @@ static ssize_t lbs_debugfs_write(struct file *f, const char __user *buf,
        char *p2;
        struct debug_data *d = f->private_data;
 
-       pdata = kmalloc(cnt, GFP_KERNEL);
+       if (cnt == 0)
+               return 0;
+
+       pdata = kmalloc(cnt + 1, GFP_KERNEL);
        if (pdata == NULL)
                return 0;
 
@@ -928,6 +931,7 @@ static ssize_t lbs_debugfs_write(struct file *f, const char __user *buf,
                kfree(pdata);
                return 0;
        }
+       pdata[cnt] = '\0';
 
        p0 = pdata;
        for (i = 0; i < num_of_items; i++) {