syscalls: add openat2()

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/configure.ac b/configure.ac
index 70099e3ad07a83240bc0d9c26bdb2122304df306..f58487f5d049d2c7e9b76140085feedb78997afd 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -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>]])

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 36a2309a43529a9c88ab73b893fa2e9d10b70557..2e513d1cc7bd0c538f01387ccabcf3109978e81c 100644 (file)
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -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);

diff --git a/src/lxc/syscall_numbers.h b/src/lxc/syscall_numbers.h
index 72e4ffe46015da69cb18d5c9becb71df2b09cc1f..8305173d6be670d6b447961bcb3913e90f1c7485 100644 (file)
--- a/src/lxc/syscall_numbers.h
+++ b/src/lxc/syscall_numbers.h
@@ -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 */

diff --git a/src/lxc/syscall_wrappers.h b/src/lxc/syscall_wrappers.h
index 6aaa43722622a488361cfed9730d7ff6ef443051..37aa76c2841229a18e88d22e209c61668fb9ceef 100644 (file)
--- a/src/lxc/syscall_wrappers.h
+++ b/src/lxc/syscall_wrappers.h
@@ -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 */