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module: Factor out elf_validity_cache_index_str

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Pull out index validation for the symbol string section.

Note that this does not validate the *contents* of the string table,
only shape and presence of the section.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
This commit is contained in:
Matthew Maurer 2024-10-15 23:16:42 +00:00 committed by Luis Chamberlain
parent 9bd4982cf7
commit 0a93953344
1 changed files with 28 additions and 9 deletions
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37
kernel/module/main.c
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@ -2014,6 +2014,31 @@ static int elf_validity_cache_index_sym(struct load_info *info)
return 0;
}
/**
* elf_validity_cache_index_str() - Validate and cache strtab index
* @info: Load info to cache strtab index in.
* Must have &load_info->sechdrs and &load_info->secstrings populated.
* Must have &load_info->index.sym populated.
*
* Looks at the symbol table's associated string table, makes sure it is
* in-bounds, and caches it.
*
* Return: %0 if valid, %-ENOEXEC on failure.
*/
static int elf_validity_cache_index_str(struct load_info *info)
{
unsigned int str_idx = info->sechdrs[info->index.sym].sh_link;
if (str_idx == SHN_UNDEF || str_idx >= info->hdr->e_shnum) {
pr_err("Invalid ELF sh_link!=SHN_UNDEF(%d) or (sh_link(%d) >= hdr->e_shnum(%d)\n",
str_idx, str_idx, info->hdr->e_shnum);
return -ENOEXEC;
}
info->index.str = str_idx;
return 0;
}
/*
* Check userspace passed ELF module against our expectations, and cache
* useful variables for further processing as we go.
@ -2037,7 +2062,6 @@ static int elf_validity_cache_index_sym(struct load_info *info)
static int elf_validity_cache_copy(struct load_info *info, int flags)
{
int err;
int str_idx;
err = elf_validity_cache_sechdrs(info);
if (err < 0)
@ -2054,16 +2078,11 @@ static int elf_validity_cache_copy(struct load_info *info, int flags)
err = elf_validity_cache_index_sym(info);
if (err < 0)
return err;
str_idx = info->sechdrs[info->index.sym].sh_link;
if (str_idx == SHN_UNDEF || str_idx >= info->hdr->e_shnum) {
pr_err("Invalid ELF sh_link!=SHN_UNDEF(%d) or (sh_link(%d) >= hdr->e_shnum(%d)\n",
str_idx, str_idx, info->hdr->e_shnum);
return -ENOEXEC;
}
err = elf_validity_cache_index_str(info);
if (err < 0)
return err;
/* Sets internal strings. */
info->index.str = str_idx;
info->strtab = (char *)info->hdr + info->sechdrs[info->index.str].sh_offset;
/* This is temporary: point mod into copy of data. */