Re: [Crash-utility] [PATCH] Fix a segfault in setup_ikconfig.

Hi Anderson, I want to introduce a patch to your crash tool project. It’s a bugfix for a segfault in setup_ikconfig. We add an ikconfig entry only if ent[0] != '#', it is not an advisable condition because there is a potential segfault risk if ent is gibberish. I explain the reproducing steps about this segfault case: I try to apply the following patch to crash 7.2.6++ code for a test. --- a/arm64.c +++ b/arm64.c @@ -32,6 +32,7 @@ static int verify_kimage_voffset(void); static void arm64_calc_kimage_voffset(void); static void arm64_calc_phys_offset(void); static void arm64_calc_virtual_memory_ranges(void); +static void arm64_get_section_size_bits(void); static int arm64_kdump_phys_base(ulong *); static ulong arm64_processor_speed(void); static void arm64_init_kernel_pgd(void); @@ -375,7 +376,11 @@ arm64_init(int when) case POST_GDB: arm64_calc_virtual_memory_ranges(); - machdep->section_size_bits = _SECTION_SIZE_BITS; + arm64_get_section_size_bits(); + if (CRASHDEBUG(1)) { + fprintf(fp, "SECTION_SIZE_BITS: %ld\n", machdep->section_size_bits); + } + if (!machdep->max_physmem_bits) { if ((string = pc->read_vmcoreinfo("NUMBER(MAX_PHYSMEM_BITS)"))) { machdep->max_physmem_bits = atol(string); @@ -1055,6 +1060,32 @@ arm64_calc_phys_offset(void) fprintf(fp, "using %lx as phys_offset\n", ms->phys_offset); } +/* + * Determine SECTION_SIZE_BITS either by reading VMCOREINFO or the kernel + * config, otherwise borrow the 64-bit ARM default definiton. + */ +static void +arm64_get_section_size_bits(void) +{ + int ret; + char *string; + + if ((string = pc->read_vmcoreinfo("NUMBER(SECTION_SIZE_BITS)"))) { + machdep->section_size_bits = atol(string); + free(string); + return; + } + + if ((ret = get_kernel_config("CONFIG_MEMORY_HOTPLUG", NULL)) == IKCONFIG_Y) { + if ((ret = get_kernel_config("CONFIG_HOTPLUG_SIZE_BITS", &string)) == IKCONFIG_STR) { + machdep->section_size_bits = atol(string); + free(string); + return; + } + } else { + machdep->section_size_bits = _SECTION_SIZE_BITS; + } +} Then I make and load the dumpfiles by crash, it occurs a segment fault as below: crash[31000]: segfault at 0 ip 00007f0fb24d98d1 sp 00007fff1703f7e8 error 4 in libc-2.26.so[7f0fb235b000+1d6000] So I add debug to find out the segfault reason, It occurred in setup_ikconfig-> add_ikconfig_entry. add_ikconfig_entry: ▒▒▒U //The last ent is a gibberish, lead to segfault I think the most advisable judgement is if an ikconfig entry start with "CONFIG_". I debug by the following patch and never reproduce segfault again. diff --git a/kernel.c b/kernel.c index 7804aef..d023c87 100644 --- a/kernel.c +++ b/kernel.c @@ -10144,7 +10144,7 @@ static int setup_ikconfig(char *config) while (whitespace(*ent)) ent++; - if (ent[0] != '#') { + if (!strncmp(ent, "CONFIG_", strlen("CONFIG_"))) { add_ikconfig_entry(ent, &ikconfig_all[kt->ikconfig_ents++]); if (kt->ikconfig_ents == IKCONFIG_MAX) { Thanks for your review. I’m looking forward to your favourable reply! Best regards,

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