Commit 59ef28b1 authored by Rusty Russell's avatar Rusty Russell
Browse files

module: fix out-by-one error in kallsyms 

Masaki found and patched a kallsyms issue: the last symbol in a
module's symtab wasn't transferred.  This is because we manually copy
the zero'th entry (which is always empty) then copy the rest in a loop
starting at 1, though from src[0].  His fix was minimal, I prefer to
rewrite the loops in more standard form.

There are two loops: one to get the size, and one to copy.  Make these
identical: always count entry 0 and any defined symbol in an allocated
non-init section.

This bug exists since the following commit was introduced.
   module: reduce symbol table for loaded modules (v2)
   commit: 4a496226

LKML: http://lkml.org/lkml/2012/10/24/27


Reported-by: default avatarMasaki Kimura <masaki.kimura.kz@hitachi.com>
Cc: stable@kernel.org
parent bc909421

kernel/module.c

+16 −11
Original line number Diff line number Diff line
@@ -2293,12 +2293,17 @@ static void layout_symtab(struct module *mod, struct load_info *info) 
	src = (void *)info->hdr + symsect->sh_offset;

	nsrc = symsect->sh_size / sizeof(*src);



	/* strtab always starts with a nul, so offset 0 is the empty string. */

	strtab_size = 1;



	/* Compute total space required for the core symbols' strtab. */

	for (ndst = i = strtab_size = 1; i < nsrc; ++i, ++src)

		if (is_core_symbol(src, info->sechdrs, info->hdr->e_shnum)) {

			strtab_size += strlen(&info->strtab[src->st_name]) + 1;

	for (ndst = i = 0; i < nsrc; i++) {

		if (i == 0 ||

		    is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum)) {

			strtab_size += strlen(&info->strtab[src[i].st_name])+1;

			ndst++;

		}

	}



	/* Append room for core symbols at end of core part. */

	info->symoffs = ALIGN(mod->core_size, symsect->sh_addralign ?: 1);
@@ -2332,15 +2337,15 @@ static void add_kallsyms(struct module *mod, const struct load_info *info) 
	mod->core_symtab = dst = mod->module_core + info->symoffs;

	mod->core_strtab = s = mod->module_core + info->stroffs;

	src = mod->symtab;

	*dst = *src;

	*s++ = 0;

	for (ndst = i = 1; i < mod->num_symtab; ++i, ++src) {

		if (!is_core_symbol(src, info->sechdrs, info->hdr->e_shnum))

			continue;



		dst[ndst] = *src;

	for (ndst = i = 0; i < mod->num_symtab; i++) {

		if (i == 0 ||

		    is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum)) {

			dst[ndst] = src[i];

			dst[ndst++].st_name = s - mod->core_strtab;

		s += strlcpy(s, &mod->strtab[src->st_name], KSYM_NAME_LEN) + 1;

			s += strlcpy(s, &mod->strtab[src[i].st_name],

				     KSYM_NAME_LEN) + 1;

		}

	}

	mod->core_num_syms = ndst;

}

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