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    Subject[PATCH 048/241] module: fix out-by-one error in kallsyms
    Date
    3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Rusty Russell <rusty@rustcorp.com.au>

    commit 59ef28b1f14899b10d6b2682c7057ca00a9a3f47 upstream.

    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: 4a4962263f07d14660849ec134ee42b63e95ea9a

    LKML: http://lkml.org/lkml/2012/10/24/27
    Reported-by: Masaki Kimura <masaki.kimura.kz@hitachi.com>
    Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
    ---
    kernel/module.c | 27 ++++++++++++++++-----------
    1 file changed, 16 insertions(+), 11 deletions(-)

    diff --git a/kernel/module.c b/kernel/module.c
    index 9ad9ee9..2a15c59 100644
    --- a/kernel/module.c
    +++ b/kernel/module.c
    @@ -2273,12 +2273,17 @@ 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);
    @@ -2312,15 +2317,15 @@ 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;
    - dst[ndst++].st_name = s - mod->core_strtab;
    - s += strlcpy(s, &mod->strtab[src->st_name], KSYM_NAME_LEN) + 1;
    + 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[i].st_name],
    + KSYM_NAME_LEN) + 1;
    + }
    }
    mod->core_num_syms = ndst;
    }
    --
    1.7.9.5


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