[Crash-utility] Increase NR_CPUS

[Maneesh Soni <maneesh@xxxxxxxxxx>]

Hi Dave,

crash seg faults while opening a kdump with NR_CPUS=128, due to buffer overflow
in max_cpudata_limit() on a i386 system. 

--------
kmem_cache_s_array_nodes:

        if (!readmem(cache+OFFSET(kmem_cache_s_array),
            KVADDR, &cpudata[0],
            sizeof(ulong) * ARRAY_LENGTH(kmem_cache_s_array),
            "array cache array", RETURN_ON_ERROR))
                goto bail_out;

        for (i = max_limit = 0; (i < ARRAY_LENGTH(kmem_cache_s_array)) &&
             cpudata[i]; i++) {
                if (!readmem(cpudata[i]+OFFSET(array_cache_limit),
                    KVADDR, &limit, sizeof(int),
                    "array cache limit", RETURN_ON_ERROR))
                        goto bail_out;
                if (limit > max_limit)
                        max_limit = limit;
        }

        *cpus = i;    <<<<<< faults here
--------

The first readmem() call overwrites the parameter "cpus" on stack. ARRAY_LENGTH
gives 128 whereas we have 32 elements in cpudata[NR_CPUS].

Though the default NR_CPUS in kernel source is 32 but it can go upto
256 based on the kernel config option CONFIG_NR_CPUS. So, in crash it
should be defined as the max NR_CPUS. Please find the patch below which
makes sure to have max NR_CPUS for various architecture.


--- crash-4.0-2.30/defs.h	2006-06-07 01:16:33.000000000 +0530
+++ crash-4.0-2.30-fix/defs.h	2006-06-24 04:29:35.000000000 +0530
@@ -56,7 +56,7 @@
 #define FALSE (0)
 
 #ifdef X86
-#define NR_CPUS  (32)
+#define NR_CPUS  (256)
 #endif
 #ifdef X86_64
 #define NR_CPUS  (256)
@@ -68,7 +68,7 @@
 #define NR_CPUS  (32)
 #endif
 #ifdef IA64
-#define NR_CPUS  (512)
+#define NR_CPUS  (1024)
 #endif
 #ifdef PPC64
 #define NR_CPUS  (128)


Thanks
Maneesh