d740269867
To avoid an explosion of request_module calls on a chain of abusive
scripts, fail maximum recursion with -ELOOP instead of -ENOEXEC. As soon
as maximum recursion depth is hit, the error will fail all the way back
up the chain, aborting immediately.
This also has the side-effect of stopping the user's shell from attempting
to reexecute the top-level file as a shell script. As seen in the
dash source:
if (cmd != path_bshell && errno == ENOEXEC) {
*argv-- = cmd;
*argv = cmd = path_bshell;
goto repeat;
}
The above logic was designed for running scripts automatically that lacked
the "#!" header, not to re-try failed recursion. On a legitimate -ENOEXEC,
things continue to behave as the shell expects.
Additionally, when tracking recursion, the binfmt handlers should not be
involved. The recursion being tracked is the depth of calls through
search_binary_handler(), so that function should be exclusively responsible
for tracking the depth.
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: halfdog <me@halfdog.net>
Cc: P J P <ppandit@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
114 lines
2.7 KiB
C
114 lines
2.7 KiB
C
/*
|
|
* linux/fs/binfmt_em86.c
|
|
*
|
|
* Based on linux/fs/binfmt_script.c
|
|
* Copyright (C) 1996 Martin von Löwis
|
|
* original #!-checking implemented by tytso.
|
|
*
|
|
* em86 changes Copyright (C) 1997 Jim Paradis
|
|
*/
|
|
|
|
#include <linux/module.h>
|
|
#include <linux/string.h>
|
|
#include <linux/stat.h>
|
|
#include <linux/binfmts.h>
|
|
#include <linux/elf.h>
|
|
#include <linux/init.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/file.h>
|
|
#include <linux/errno.h>
|
|
|
|
|
|
#define EM86_INTERP "/usr/bin/em86"
|
|
#define EM86_I_NAME "em86"
|
|
|
|
static int load_em86(struct linux_binprm *bprm)
|
|
{
|
|
char *interp, *i_name, *i_arg;
|
|
struct file * file;
|
|
int retval;
|
|
struct elfhdr elf_ex;
|
|
|
|
/* Make sure this is a Linux/Intel ELF executable... */
|
|
elf_ex = *((struct elfhdr *)bprm->buf);
|
|
|
|
if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
|
|
return -ENOEXEC;
|
|
|
|
/* First of all, some simple consistency checks */
|
|
if ((elf_ex.e_type != ET_EXEC && elf_ex.e_type != ET_DYN) ||
|
|
(!((elf_ex.e_machine == EM_386) || (elf_ex.e_machine == EM_486))) ||
|
|
(!bprm->file->f_op || !bprm->file->f_op->mmap)) {
|
|
return -ENOEXEC;
|
|
}
|
|
|
|
allow_write_access(bprm->file);
|
|
fput(bprm->file);
|
|
bprm->file = NULL;
|
|
|
|
/* Unlike in the script case, we don't have to do any hairy
|
|
* parsing to find our interpreter... it's hardcoded!
|
|
*/
|
|
interp = EM86_INTERP;
|
|
i_name = EM86_I_NAME;
|
|
i_arg = NULL; /* We reserve the right to add an arg later */
|
|
|
|
/*
|
|
* Splice in (1) the interpreter's name for argv[0]
|
|
* (2) (optional) argument to interpreter
|
|
* (3) filename of emulated file (replace argv[0])
|
|
*
|
|
* This is done in reverse order, because of how the
|
|
* user environment and arguments are stored.
|
|
*/
|
|
remove_arg_zero(bprm);
|
|
retval = copy_strings_kernel(1, &bprm->filename, bprm);
|
|
if (retval < 0) return retval;
|
|
bprm->argc++;
|
|
if (i_arg) {
|
|
retval = copy_strings_kernel(1, &i_arg, bprm);
|
|
if (retval < 0) return retval;
|
|
bprm->argc++;
|
|
}
|
|
retval = copy_strings_kernel(1, &i_name, bprm);
|
|
if (retval < 0) return retval;
|
|
bprm->argc++;
|
|
|
|
/*
|
|
* OK, now restart the process with the interpreter's inode.
|
|
* Note that we use open_exec() as the name is now in kernel
|
|
* space, and we don't need to copy it.
|
|
*/
|
|
file = open_exec(interp);
|
|
if (IS_ERR(file))
|
|
return PTR_ERR(file);
|
|
|
|
bprm->file = file;
|
|
|
|
retval = prepare_binprm(bprm);
|
|
if (retval < 0)
|
|
return retval;
|
|
|
|
return search_binary_handler(bprm);
|
|
}
|
|
|
|
static struct linux_binfmt em86_format = {
|
|
.module = THIS_MODULE,
|
|
.load_binary = load_em86,
|
|
};
|
|
|
|
static int __init init_em86_binfmt(void)
|
|
{
|
|
register_binfmt(&em86_format);
|
|
return 0;
|
|
}
|
|
|
|
static void __exit exit_em86_binfmt(void)
|
|
{
|
|
unregister_binfmt(&em86_format);
|
|
}
|
|
|
|
core_initcall(init_em86_binfmt);
|
|
module_exit(exit_em86_binfmt);
|
|
MODULE_LICENSE("GPL");
|