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syscalls: add openat2()

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Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This commit is contained in:
Christian Brauner 2020-08-09 12:48:02 +02:00
parent da0fdceb6d
commit 2b0c810617
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GPG Key ID: 8EB056D53EECB12D
4 changed files with 85 additions and 2 deletions
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3
configure.ac
View File

@ -622,7 +622,8 @@ AC_CHECK_HEADER([ifaddrs.h],
AC_HEADER_MAJOR
# Check for some syscalls functions
AC_CHECK_FUNCS([setns pivot_root sethostname unshare rand_r confstr faccessat gettid memfd_create move_mount open_tree execveat clone3 fsopen fspick fsconfig fsmount])
AC_CHECK_FUNCS([setns pivot_root sethostname unshare rand_r confstr faccessat gettid memfd_create move_mount open_tree execveat clone3 fsopen fspick fsconfig fsmount, openat2])
AC_CHECK_TYPES([struct open_how], [], [], [[#include <linux/openat2.h>]])
AC_CHECK_TYPES([struct clone_args], [], [], [[#include <linux/sched.h>]])
AC_CHECK_MEMBERS([struct clone_args.set_tid],[],[],[[#include <linux/sched.h>]])
AC_CHECK_MEMBERS([struct clone_args.cgroup],[],[],[[#include <linux/sched.h>]])

2
src/lxc/conf.c
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@ -1077,7 +1077,7 @@ static int mount_autodev(const char *name, const struct lxc_rootfs *rootfs,
goto reset_umask;
}
ret = safe_mount("none", path, "tmpfs", 0, mount_options,
ret = safe_mount("none", "dev", "tmpfs", 0, mount_options,
rootfs->path ? rootfs->mount : NULL );
if (ret < 0) {
SYSERROR("Failed to mount tmpfs on \"%s\"", path);

20
src/lxc/syscall_numbers.h
View File

@ -640,4 +640,24 @@
#endif
#endif
#ifndef __NR_openat2
#if defined __alpha__
#define __NR_openat2 547
#elif defined _MIPS_SIM
#if _MIPS_SIM == _MIPS_SIM_ABI32 /* o32 */
#define __NR_openat2 4437
#endif
#if _MIPS_SIM == _MIPS_SIM_NABI32 /* n32 */
#define __NR_openat2 6437
#endif
#if _MIPS_SIM == _MIPS_SIM_ABI64 /* n64 */
#define __NR_openat2 5437
#endif
#elif defined __ia64__
#define __NR_openat2 (437 + 1024)
#else
#define __NR_openat2 437
#endif
#endif
#endif /* __LXC_SYSCALL_NUMBERS_H */

62
src/lxc/syscall_wrappers.h
View File

@ -16,6 +16,7 @@
#include <unistd.h>
#include "config.h"
#include "macro.h"
#include "syscall_numbers.h"
#ifdef HAVE_LINUX_MEMFD_H
@ -26,6 +27,10 @@
#include <sys/signalfd.h>
#endif
#ifdef HAVE_STRUCT_OPEN_HOW
#include <linux/openat2.h>
#endif
typedef int32_t key_serial_t;
#if !HAVE_KEYCTL
@ -203,4 +208,61 @@ static inline int fsmount_lxc(int fs_fd, unsigned int flags, unsigned int attr_f
extern int fsmount(int fs_fd, unsigned int flags, unsigned int attr_flags);
#endif
/*
* Arguments for how openat2(2) should open the target path. If only @flags and
* @mode are non-zero, then openat2(2) operates very similarly to openat(2).
*
* However, unlike openat(2), unknown or invalid bits in @flags result in
* -EINVAL rather than being silently ignored. @mode must be zero unless one of
* {O_CREAT, O_TMPFILE} are set.
*
* @flags: O_* flags.
* @mode: O_CREAT/O_TMPFILE file mode.
* @resolve: RESOLVE_* flags.
*/
struct lxc_open_how {
__u64 flags;
__u64 mode;
__u64 resolve;
};
/* how->resolve flags for openat2(2). */
#ifndef RESOLVE_NO_XDEV
#define RESOLVE_NO_XDEV 0x01 /* Block mount-point crossings
(includes bind-mounts). */
#endif
#ifndef RESOLVE_NO_MAGICLINKS
#define RESOLVE_NO_MAGICLINKS 0x02 /* Block traversal through procfs-style
"magic-links". */
#endif
#ifndef RESOLVE_NO_SYMLINKS
#define RESOLVE_NO_SYMLINKS 0x04 /* Block traversal through all symlinks
(implies OEXT_NO_MAGICLINKS) */
#endif
#ifndef RESOLVE_BENEATH
#define RESOLVE_BENEATH 0x08 /* Block "lexical" trickery like
"..", symlinks, and absolute
paths which escape the dirfd. */
#endif
#ifndef RESOLVE_IN_ROOT
#define RESOLVE_IN_ROOT 0x10 /* Make all jumps to "/" and ".."
be scoped inside the dirfd
(similar to chroot(2)). */
#endif
#ifndef HAVE_OPENAT2
static inline int openat2(int dfd, const char *filename, struct lxc_open_how *how, size_t size)
{
/* When struct open_how is updated we should update lxc as well. */
#ifdef HAVE_STRUCT_OPEN_HOW
BUILD_BUG_ON(sizeof(struct lxc_open_how) != sizeof(struct open_how));
#endif
return syscall(__NR_openat2, dfd, filename, (struct open_how *)how, size);
}
#endif /* HAVE_OPENAT2 */
#endif /* __LXC_SYSCALL_WRAPPER_H */