[Crash-utility] [External Mail]Re: [PATCH] Fix a segfault in setup_ikconfig.
陈启武
chenqiwu at xiaomi.com
Wed Sep 18 02:14:30 UTC 2019
Hi Dave,
1. I'm requesting the arm64.c change as well. Because some chip makers would like to define their own section size bits in kernel config to support memory hotplug, which is not same as ARM64 default SECTION_SIZE_BITS value: 30, such as QCOM SDM8150 or 8250 borads. Although linux kernel maintain line still define default SECTION_SIZE_BITS value: 30 as section_size_bits for sparsemem. The patch has detailed descript in the email "[PATCH] Fix for the determination of the ARM64 SECTION_SIZE_BITS".
2. The output of "sys config" for my dumpfile has been uploaded, which shows the last line is empty. it occurs a segment fault when add the last empty line into ikconfig entry. I agree that the use of STRNEQ() is better than strncmp().
Best regards,
Qiwu
-----Original Message-----
From: Dave Anderson <anderson at redhat.com>
Sent: Wednesday, September 18, 2019 3:22 AM
To: 陈启武 <chenqiwu at xiaomi.com>
Cc: crash-utility at redhat.com
Subject: [External Mail]Re: [PATCH] Fix a segfault in setup_ikconfig.
----- Original Message -----
>
> 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.
Using your dumpfile that has the bogus "ent" string, can you show me what the output of "sys config" looks like?
Dave
> 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
>
>
>
>
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