[Xen-changelog] Proactively check for NULL strings passed into xc_linux_build. Either DTRT

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User emellor@xxxxxxxxxxxxxxxxxxxxxx
# Node ID 0a69deed5e1fbd7627f6c73a6ca494abb0ad0be2
# Parent  fbee8d9fbabae6a7a966a49f9fc4104e4fd9d97a
Proactively check for NULL strings passed into xc_linux_build.  Either DTRT
or return error if detected.  A NULL cmdline, for example, would currently
generate a segfault.

Signed-off-by: Ben Thomas  <bjthomas3@xxxxxxxxx>

diff -r fbee8d9fbaba -r 0a69deed5e1f tools/libxc/xc_linux_build.c
--- a/tools/libxc/xc_linux_build.c      Tue Jan 10 14:33:00 2006
+++ b/tools/libxc/xc_linux_build.c      Tue Jan 10 14:37:25 2006
@@ -693,8 +693,11 @@
         start_info->mod_start    = vinitrd_start;
         start_info->mod_len      = initrd_len;
     }
-    strncpy((char *)start_info->cmd_line, cmdline, MAX_GUEST_CMDLINE);
-    start_info->cmd_line[MAX_GUEST_CMDLINE-1] = '\0';
+    if (cmdline != NULL) {
+        strncpy((char *)start_info->cmd_line, cmdline, MAX_GUEST_CMDLINE);
+        start_info->cmd_line[MAX_GUEST_CMDLINE-1] = '\0';
+    } else
+        start_info->cmd_line[0] = '\0';
     munmap(start_info, PAGE_SIZE);
 
     /* shared_info page starts its life empty. */
@@ -755,7 +758,8 @@
         goto error_out;
     }
 
-    if ( (image = xc_read_kernel_image(image_name, &image_size)) == NULL )
+    if ( (image_name == NULL) ||
+         ((image = xc_read_kernel_image(image_name, &image_size)) == NULL) )
         goto error_out;
 
     if ( (ramdisk_name != NULL) && (strlen(ramdisk_name) != 0) )

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