mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-21 16:29:59 +00:00
![David Drysdale](/assets/img/avatar_default.png)
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>
123 lines
4 KiB
C
123 lines
4 KiB
C
#ifndef _LINUX_BINFMTS_H
|
|
#define _LINUX_BINFMTS_H
|
|
|
|
#include <linux/sched.h>
|
|
#include <linux/unistd.h>
|
|
#include <asm/exec.h>
|
|
#include <uapi/linux/binfmts.h>
|
|
|
|
#define CORENAME_MAX_SIZE 128
|
|
|
|
/*
|
|
* This structure is used to hold the arguments that are used when loading binaries.
|
|
*/
|
|
struct linux_binprm {
|
|
char buf[BINPRM_BUF_SIZE];
|
|
#ifdef CONFIG_MMU
|
|
struct vm_area_struct *vma;
|
|
unsigned long vma_pages;
|
|
#else
|
|
# define MAX_ARG_PAGES 32
|
|
struct page *page[MAX_ARG_PAGES];
|
|
#endif
|
|
struct mm_struct *mm;
|
|
unsigned long p; /* current top of mem */
|
|
unsigned int
|
|
cred_prepared:1,/* true if creds already prepared (multiple
|
|
* preps happen for interpreters) */
|
|
cap_effective:1;/* true if has elevated effective capabilities,
|
|
* false if not; except for init which inherits
|
|
* its parent's caps anyway */
|
|
#ifdef __alpha__
|
|
unsigned int taso:1;
|
|
#endif
|
|
unsigned int recursion_depth; /* only for search_binary_handler() */
|
|
struct file * file;
|
|
struct cred *cred; /* new credentials */
|
|
int unsafe; /* how unsafe this exec is (mask of LSM_UNSAFE_*) */
|
|
unsigned int per_clear; /* bits to clear in current->personality */
|
|
int argc, envc;
|
|
const char * filename; /* Name of binary as seen by procps */
|
|
const char * interp; /* Name of the binary really executed. Most
|
|
of the time same as filename, but could be
|
|
different for binfmt_{misc,script} */
|
|
unsigned interp_flags;
|
|
unsigned interp_data;
|
|
unsigned long loader, exec;
|
|
};
|
|
|
|
#define BINPRM_FLAGS_ENFORCE_NONDUMP_BIT 0
|
|
#define BINPRM_FLAGS_ENFORCE_NONDUMP (1 << BINPRM_FLAGS_ENFORCE_NONDUMP_BIT)
|
|
|
|
/* fd of the binary should be passed to the interpreter */
|
|
#define BINPRM_FLAGS_EXECFD_BIT 1
|
|
#define BINPRM_FLAGS_EXECFD (1 << BINPRM_FLAGS_EXECFD_BIT)
|
|
|
|
/* filename of the binary will be inaccessible after exec */
|
|
#define BINPRM_FLAGS_PATH_INACCESSIBLE_BIT 2
|
|
#define BINPRM_FLAGS_PATH_INACCESSIBLE (1 << BINPRM_FLAGS_PATH_INACCESSIBLE_BIT)
|
|
|
|
/* Function parameter for binfmt->coredump */
|
|
struct coredump_params {
|
|
const siginfo_t *siginfo;
|
|
struct pt_regs *regs;
|
|
struct file *file;
|
|
unsigned long limit;
|
|
unsigned long mm_flags;
|
|
loff_t written;
|
|
};
|
|
|
|
/*
|
|
* This structure defines the functions that are used to load the binary formats that
|
|
* linux accepts.
|
|
*/
|
|
struct linux_binfmt {
|
|
struct list_head lh;
|
|
struct module *module;
|
|
int (*load_binary)(struct linux_binprm *);
|
|
int (*load_shlib)(struct file *);
|
|
int (*core_dump)(struct coredump_params *cprm);
|
|
unsigned long min_coredump; /* minimal dump size */
|
|
};
|
|
|
|
extern void __register_binfmt(struct linux_binfmt *fmt, int insert);
|
|
|
|
/* Registration of default binfmt handlers */
|
|
static inline void register_binfmt(struct linux_binfmt *fmt)
|
|
{
|
|
__register_binfmt(fmt, 0);
|
|
}
|
|
/* Same as above, but adds a new binfmt at the top of the list */
|
|
static inline void insert_binfmt(struct linux_binfmt *fmt)
|
|
{
|
|
__register_binfmt(fmt, 1);
|
|
}
|
|
|
|
extern void unregister_binfmt(struct linux_binfmt *);
|
|
|
|
extern int prepare_binprm(struct linux_binprm *);
|
|
extern int __must_check remove_arg_zero(struct linux_binprm *);
|
|
extern int search_binary_handler(struct linux_binprm *);
|
|
extern int flush_old_exec(struct linux_binprm * bprm);
|
|
extern void setup_new_exec(struct linux_binprm * bprm);
|
|
extern void would_dump(struct linux_binprm *, struct file *);
|
|
|
|
extern int suid_dumpable;
|
|
|
|
/* Stack area protections */
|
|
#define EXSTACK_DEFAULT 0 /* Whatever the arch defaults to */
|
|
#define EXSTACK_DISABLE_X 1 /* Disable executable stacks */
|
|
#define EXSTACK_ENABLE_X 2 /* Enable executable stacks */
|
|
|
|
extern int setup_arg_pages(struct linux_binprm * bprm,
|
|
unsigned long stack_top,
|
|
int executable_stack);
|
|
extern int bprm_change_interp(char *interp, struct linux_binprm *bprm);
|
|
extern int copy_strings_kernel(int argc, const char *const *argv,
|
|
struct linux_binprm *bprm);
|
|
extern int prepare_bprm_creds(struct linux_binprm *bprm);
|
|
extern void install_exec_creds(struct linux_binprm *bprm);
|
|
extern void set_binfmt(struct linux_binfmt *new);
|
|
extern ssize_t read_code(struct file *, unsigned long, loff_t, size_t);
|
|
|
|
#endif /* _LINUX_BINFMTS_H */
|