3a2e7f47d7
This can be triggered with root help only, but... Register the ":text:E::txt::/root/cat.txt:' rule in binfmt_misc (by root) and try launching the cat.txt file (by anyone) :) The result is - the endless recursion in the load_misc_binary -> open_exec -> load_misc_binary chain and stack overflow. There's a similar problem with binfmt_script, and there's a sh_bang memner on linux_binprm structure to handle this, but simply raising this in binfmt_misc may break some setups when the interpreter of some misc binaries is a script. So the proposal is to turn sh_bang into a bit, add a new one (the misc_bang) and raise it in load_misc_binary. After this, even if we set up the misc -> script -> misc loop for binfmts one of them will step on its own bang and exit. Signed-off-by: Pavel Emelyanov <xemul@openvz.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
114 lines
2.8 KiB
C
114 lines
2.8 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/slab.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,struct pt_regs *regs)
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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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bprm->sh_bang = 1; /* Well, the bang-shell is implicit... */
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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, regs);
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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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return register_binfmt(&em86_format);
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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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