forked from luck/tmp_suning_uos_patched
51f39a1f0c
This patchset adds execveat(2) for x86, and is derived from Meredydd Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528). The primary aim of adding an execveat syscall is to allow an implementation of fexecve(3) that does not rely on the /proc filesystem, at least for executables (rather than scripts). The current glibc version of fexecve(3) is implemented via /proc, which causes problems in sandboxed or otherwise restricted environments. Given the desire for a /proc-free fexecve() implementation, HPA suggested (https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be an appropriate generalization. Also, having a new syscall means that it can take a flags argument without back-compatibility concerns. The current implementation just defines the AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be added in future -- for example, flags for new namespaces (as suggested at https://lkml.org/lkml/2006/7/11/474). Related history: - https://lkml.org/lkml/2006/12/27/123 is an example of someone realizing that fexecve() is likely to fail in a chroot environment. - http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered documenting the /proc requirement of fexecve(3) in its manpage, to "prevent other people from wasting their time". - https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a problem where a process that did setuid() could not fexecve() because it no longer had access to /proc/self/fd; this has since been fixed. This patch (of 4): Add a new execveat(2) system call. execveat() is to execve() as openat() is to open(): it takes a file descriptor that refers to a directory, and resolves the filename relative to that. In addition, if the filename is empty and AT_EMPTY_PATH is specified, execveat() executes the file to which the file descriptor refers. This replicates the functionality of fexecve(), which is a system call in other UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and so relies on /proc being mounted). The filename fed to the executed program as argv[0] (or the name of the script fed to a script interpreter) will be of the form "/dev/fd/<fd>" (for an empty filename) or "/dev/fd/<fd>/<filename>", effectively reflecting how the executable was found. This does however mean that execution of a script in a /proc-less environment won't work; also, script execution via an O_CLOEXEC file descriptor fails (as the file will not be accessible after exec). Based on patches by Meredydd Luff. Signed-off-by: David Drysdale <drysdale@google.com> Cc: Meredydd Luff <meredydd@senatehouse.org> Cc: Shuah Khan <shuah.kh@samsung.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Rich Felker <dalias@aerifal.cx> Cc: Christoph Hellwig <hch@infradead.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
118 lines
2.8 KiB
C
118 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/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->mmap) {
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return -ENOEXEC;
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}
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/* Need to be able to load the file after exec */
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if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
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return -ENOENT;
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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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