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module: Factor out elf_validity_cache_index_sym

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Centralize symbol table detection and property validation.

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 23:16:41 +00:00 committed by Luis Chamberlain
parent 0be41a9367
commit 9bd4982cf7
1 changed files with 44 additions and 29 deletions
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73
kernel/module/main.c
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@ -1980,6 +1980,39 @@ static int elf_validity_cache_index_mod(struct load_info *info)
return 0;
}
/**
* elf_validity_cache_index_sym() - Validate and cache symtab index
* @info: Load info to cache symtab index in.
* Must have &load_info->sechdrs and &load_info->secstrings populated.
*
* Checks that there is exactly one symbol table, then caches its index in
* &load_info->index.sym.
*
* Return: %0 if valid, %-ENOEXEC on failure.
*/
static int elf_validity_cache_index_sym(struct load_info *info)
{
unsigned int sym_idx;
unsigned int num_sym_secs = 0;
int i;
for (i = 1; i < info->hdr->e_shnum; i++) {
if (info->sechdrs[i].sh_type == SHT_SYMTAB) {
num_sym_secs++;
sym_idx = i;
}
}
if (num_sym_secs != 1) {
pr_warn("%s: module has no symbols (stripped?)\n",
info->name ?: "(missing .modinfo section or name field)");
return -ENOEXEC;
}
info->index.sym = sym_idx;
return 0;
}
/*
* Check userspace passed ELF module against our expectations, and cache
@ -2003,10 +2036,8 @@ static int elf_validity_cache_index_mod(struct load_info *info)
*/
static int elf_validity_cache_copy(struct load_info *info, int flags)
{
unsigned int i;
Elf_Shdr *shdr;
int err;
unsigned int num_sym_secs = 0, sym_idx;
int str_idx;
err = elf_validity_cache_sechdrs(info);
if (err < 0)
@ -2018,34 +2049,21 @@ static int elf_validity_cache_copy(struct load_info *info, int flags)
if (err < 0)
return err;
err = elf_validity_cache_index_mod(info);
if (err < 0)
return err;
err = elf_validity_cache_index_sym(info);
if (err < 0)
return err;
for (i = 1; i < info->hdr->e_shnum; i++) {
shdr = &info->sechdrs[i];
if (shdr->sh_type == SHT_SYMTAB) {
if (shdr->sh_link == SHN_UNDEF
|| shdr->sh_link >= info->hdr->e_shnum) {
pr_err("Invalid ELF sh_link!=SHN_UNDEF(%d) or (sh_link(%d) >= hdr->e_shnum(%d)\n",
shdr->sh_link, shdr->sh_link,
info->hdr->e_shnum);
goto no_exec;
}
num_sym_secs++;
sym_idx = i;
}
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;
}
if (num_sym_secs != 1) {
pr_warn("%s: module has no symbols (stripped?)\n",
info->name ?: "(missing .modinfo section or name field)");
goto no_exec;
}
/* Sets internal symbols and strings. */
info->index.sym = sym_idx;
shdr = &info->sechdrs[sym_idx];
info->index.str = shdr->sh_link;
/* 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. */
@ -2066,9 +2084,6 @@ static int elf_validity_cache_copy(struct load_info *info, int flags)
info->index.pcpu = find_pcpusec(info);
return 0;
no_exec:
return -ENOEXEC;
}
#define COPY_CHUNK_SIZE (16*PAGE_SIZE)