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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>
113 lines
2.7 KiB
C
113 lines
2.7 KiB
C
/*
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* linux/fs/binfmt_em86.c
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*
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* Based on linux/fs/binfmt_script.c
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* Copyright (C) 1996 Martin von Löwis
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* original #!-checking implemented by tytso.
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*
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* em86 changes Copyright (C) 1997 Jim Paradis
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*/
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#include <linux/module.h>
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#include <linux/string.h>
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#include <linux/stat.h>
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#include <linux/binfmts.h>
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#include <linux/elf.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/errno.h>
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#define EM86_INTERP "/usr/bin/em86"
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#define EM86_I_NAME "em86"
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static int load_em86(struct linux_binprm *bprm)
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{
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char *interp, *i_name, *i_arg;
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struct file * file;
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int retval;
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struct elfhdr elf_ex;
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/* Make sure this is a Linux/Intel ELF executable... */
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elf_ex = *((struct elfhdr *)bprm->buf);
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if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
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return -ENOEXEC;
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/* First of all, some simple consistency checks */
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if ((elf_ex.e_type != ET_EXEC && elf_ex.e_type != ET_DYN) ||
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(!((elf_ex.e_machine == EM_386) || (elf_ex.e_machine == EM_486))) ||
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(!bprm->file->f_op || !bprm->file->f_op->mmap)) {
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return -ENOEXEC;
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}
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allow_write_access(bprm->file);
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fput(bprm->file);
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bprm->file = NULL;
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/* Unlike in the script case, we don't have to do any hairy
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* parsing to find our interpreter... it's hardcoded!
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*/
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interp = EM86_INTERP;
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i_name = EM86_I_NAME;
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i_arg = NULL; /* We reserve the right to add an arg later */
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/*
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* Splice in (1) the interpreter's name for argv[0]
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* (2) (optional) argument to interpreter
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* (3) filename of emulated file (replace argv[0])
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*
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* This is done in reverse order, because of how the
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* user environment and arguments are stored.
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*/
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remove_arg_zero(bprm);
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retval = copy_strings_kernel(1, &bprm->filename, bprm);
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if (retval < 0) return retval;
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bprm->argc++;
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if (i_arg) {
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retval = copy_strings_kernel(1, &i_arg, bprm);
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if (retval < 0) return retval;
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bprm->argc++;
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}
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retval = copy_strings_kernel(1, &i_name, bprm);
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if (retval < 0) return retval;
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bprm->argc++;
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/*
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* OK, now restart the process with the interpreter's inode.
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* Note that we use open_exec() as the name is now in kernel
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* space, and we don't need to copy it.
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*/
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file = open_exec(interp);
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if (IS_ERR(file))
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return PTR_ERR(file);
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bprm->file = file;
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retval = prepare_binprm(bprm);
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if (retval < 0)
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return retval;
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return search_binary_handler(bprm);
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}
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static struct linux_binfmt em86_format = {
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.module = THIS_MODULE,
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.load_binary = load_em86,
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};
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static int __init init_em86_binfmt(void)
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{
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register_binfmt(&em86_format);
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return 0;
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}
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static void __exit exit_em86_binfmt(void)
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{
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unregister_binfmt(&em86_format);
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}
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core_initcall(init_em86_binfmt);
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module_exit(exit_em86_binfmt);
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MODULE_LICENSE("GPL");
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