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module: add stop-grap sanity check on module memcpy()

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The integrity of the struct module we load is important, and although
our ELF validator already checks that the module section must match
struct module, add a stop-gap check before we memcpy() the final minted
module. This also makes those inspecting the code what the goal is.

While at it, clarify the goal behind updating the sh_addr address.
The current comment is pretty misleading.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
This commit is contained in:
Luis Chamberlain 2023-03-19 14:35:39 -07:00
parent 46752820f9
commit c7ee8aebf6
1 changed files with 22 additions and 4 deletions
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26
kernel/module/main.c
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@ -2213,7 +2213,8 @@ static int move_module(struct module *mod, struct load_info *info)
{
int i;
void *ptr;
enum mod_mem_type t;
enum mod_mem_type t = 0;
int ret = -ENOMEM;
for_each_mod_mem_type(type) {
if (!mod->mem[type].size) {
@ -2249,9 +2250,26 @@ static int move_module(struct module *mod, struct load_info *info)
dest = mod->mem[type].base + (shdr->sh_entsize & SH_ENTSIZE_OFFSET_MASK);
if (shdr->sh_type != SHT_NOBITS)
if (shdr->sh_type != SHT_NOBITS) {
/*
* Our ELF checker already validated this, but let's
* be pedantic and make the goal clearer. We actually
* end up copying over all modifications made to the
* userspace copy of the entire struct module.
*/
if (i == info->index.mod &&
(WARN_ON_ONCE(shdr->sh_size != sizeof(struct module)))) {
ret = -ENOEXEC;
goto out_enomem;
}
memcpy(dest, (void *)shdr->sh_addr, shdr->sh_size);
/* Update sh_addr to point to copy in image. */
}
/*
* Update the userspace copy's ELF section address to point to
* our newly allocated memory as a pure convenience so that
* users of info can keep taking advantage and using the newly
* minted official memory area.
*/
shdr->sh_addr = (unsigned long)dest;
pr_debug("\t0x%lx %s\n",
(long)shdr->sh_addr, info->secstrings + shdr->sh_name);
@ -2261,7 +2279,7 @@ static int move_module(struct module *mod, struct load_info *info)
out_enomem:
for (t--; t >= 0; t--)
module_memory_free(mod->mem[t].base, t);
return -ENOMEM;
return ret;
}
static int check_export_symbol_versions(struct module *mod)