[Crash-utility] Re: Increase NR_CPUS

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