Re: [Crash-utility] [External Mail]Re: [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, Qiwu #/******本邮件及其附件含有小米公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁止任何其他人以任何形式使用（包括但不限于全部 或部分地泄露、复制、或散发）本邮件中的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ This e-mail and its attachments contain confidential information from XIAOMI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it!******/#