linux-kernel - Re: [PATCH v7 2/4] x86/stackvalidate: Compile-time stack validation

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Date:	Tue, 21 Jul 2015 01:53:25 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>, x86@...nel.org,
	live-patching@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/4] x86/stackvalidate: Compile-time stack validation

Hi,

Just nitpicks below..


On Wed, Jul 15, 2015 at 2:14 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> +struct elf *elf_open(const char *name)
> +{
> +       struct elf *elf;
> +
> +       elf_version(EV_CURRENT);
> +
> +       elf = malloc(sizeof(*elf));
> +       if (!elf) {
> +               perror("malloc");
> +               return NULL;
> +       }
> +       memset(elf, 0, sizeof(*elf));
> +
> +       INIT_LIST_HEAD(&elf->sections);
> +
> +       elf->name = strdup(name);
> +       if (!elf->name) {
> +               perror("strdup");
> +               goto err;
> +       }
> +
> +       elf->fd = open(name, O_RDONLY);
> +       if (elf->fd == -1) {
> +               perror("open");
> +               goto err;
> +       }
> +
> +       elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
> +       if (!elf->elf) {
> +               perror("elf_begin");
> +               goto err;
> +       }
> +
> +       if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
> +               perror("gelf_getehdr");
> +               goto err;
> +       }
> +
> +       if (read_sections(elf))
> +               goto err;
> +
> +       if (read_symbols(elf))
> +               goto err;
> +
> +       if (read_relas(elf))
> +               goto err;
> +
> +       return elf;
> +
> +err:
> +       elf_close(elf);
> +       return NULL;
> +}
> +
> +void elf_close(struct elf *elf)
> +{
> +       struct section *sec, *tmpsec;
> +       struct symbol *sym, *tmpsym;
> +
> +       list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
> +               list_for_each_entry_safe(sym, tmpsym, &sec->symbols, list) {
> +                       list_del(&sym->list);
> +                       free(sym);
> +               }

It seems that it needs to free entries in sec->relas too here.


> +               list_del(&sec->list);
> +               free(sec);
> +       }
> +       if (elf->name)
> +               free(elf->name);
> +       if (elf->fd > 0)
> +               close(elf->fd);
> +       if (elf->elf)
> +               elf_end(elf->elf);
> +       free(elf);
> +}


[SNIP]

> +int main(int argc, char *argv[])
> +{
> +       struct elf *elf;
> +       int ret = 0, warnings = 0;
> +
> +       argp_parse(&argp, argc, argv, 0, 0, &args);
> +
> +       elf = elf_open(args.args[0]);
> +       if (!elf) {
> +               fprintf(stderr, "error reading elf file %s\n", args.args[0]);
> +               return 1;
> +       }
> +
> +       ret = decode_sections(elf);
> +       if (ret < 0)
> +               goto out;
> +       warnings += ret;
> +
> +       ret = validate_functions(elf);
> +       if (ret < 0)
> +               goto out;
> +       warnings += ret;
> +
> +       ret = validate_uncallable_instructions(elf);
> +       if (ret < 0)
> +               goto out;
> +       warnings += ret;
> +
> +out:

elf_close(elf);  ??

Thanks,
Namhyung


> +       /* ignore warnings for now until we get all the code cleaned up */
> +       if (ret || warnings)
> +               return 0;
> +       return 0;
> +}
> --
> 2.1.0
>
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