Kexec corrupts command line in x86-linux-setup.c setup_edd_info()

[Dmitry Trikoz]

Hi,
I've been chasing strange problem with kdump kernel. It was crashing on 
boot without any messages to the console.
Finally I found that kdump kernel command line was corrupt.
Digging down I found the problem in  setup_edd_info() and 
add_edd_entry(). It doesn't check for array size of
real_mode->eddbuf[] and real_mode->edd_mbr_sig_buffer[]
So when it overruns eddbuf[] it corrupts command_line that follows it.

Here is the fix:

--- a/kexec-tools/kexec/arch/i386/x86-linux-setup.c
+++ b/kexec-tools/kexec/arch/i386/x86-linux-setup.c
@@ -275,9 +275,9 @@ static int add_edd_entry(struct 
x86_linux_param_header *real_mode,
                                 "must not be NULL", __FUNCTION__);
                 return -1;
         }
-
-       edd_info = &real_mode->eddbuf[*current_edd];
-       memset(edd_info, 0, sizeof(struct edd_info));
+       if (*current_mbr >= EDD_MBR_SIG_MAX) {
+               return 0;
+       }

         /* extract the device number */
         if (sscanf(basename(sysfs_name), "int13_dev%hhx", &devnum) != 1) {
@@ -293,12 +293,21 @@ static int add_edd_entry(struct 
x86_linux_param_header *real_mode,
                 dbgprintf("EDD Device 0x%x: mbr_sig=0x%x\n", devnum, 
mbr_sig);
         }

+       if (*current_edd >= EDDMAXNR) {
+               return 0;
+       }
+
+       edd_info = &real_mode->eddbuf[*current_edd];
+       memset(edd_info, 0, sizeof(struct edd_info));
+
         /* set the device number */
         edd_info->device = devnum;

         /* set the version */
-       if (file_scanf(sysfs_name, "version", "0x%hhx", &version) != 1)
+       if (file_scanf(sysfs_name, "version", "0x%hhx", &version) != 1) {
+               fprintf(stderr, "sysfs_name %s version file error\n", 
sysfs_name);
                 return -1;
+       }

         edd_info->version = version;

Sincerely,

Dmitry Trikoz

dmitry.trikoz at stratus.com