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Message-Id: <20190719164225.27083-8-cyphar@cyphar.com>
Date: Sat, 20 Jul 2019 02:42:23 +1000
From: Aleksa Sarai <cyphar@...har.com>
To: Al Viro <viro@...iv.linux.org.uk>,
Jeff Layton <jlayton@...nel.org>,
"J. Bruce Fields" <bfields@...ldses.org>,
Arnd Bergmann <arnd@...db.de>,
David Howells <dhowells@...hat.com>,
Shuah Khan <shuah@...nel.org>,
Shuah Khan <skhan@...uxfoundation.org>
Cc: Aleksa Sarai <cyphar@...har.com>,
Christian Brauner <christian@...uner.io>,
Eric Biederman <ebiederm@...ssion.com>,
Andy Lutomirski <luto@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Alexei Starovoitov <ast@...nel.org>,
Kees Cook <keescook@...omium.org>,
Jann Horn <jannh@...gle.com>, Tycho Andersen <tycho@...ho.ws>,
David Drysdale <drysdale@...gle.com>,
Chanho Min <chanho.min@....com>,
Oleg Nesterov <oleg@...hat.com>, Aleksa Sarai <asarai@...e.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
containers@...ts.linux-foundation.org, linux-alpha@...r.kernel.org,
linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-fsdevel@...r.kernel.org, linux-ia64@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
linux-xtensa@...ux-xtensa.org, sparclinux@...r.kernel.org
Subject: [PATCH v10 7/9] open: openat2(2) syscall
The most obvious syscall to add support for the new LOOKUP_* scoping
flags would be openat(2). However, there are a few reasons why this is
not the best course of action:
* The new LOOKUP_* flags are intended to be security features, and
openat(2) will silently ignore all unknown flags. This means that
users would need to avoid foot-gunning themselves constantly when
using this interface if it were part of openat(2). This can be fixed
by having userspace libraries handle this for users[1], but should be
avoided if possible.
* Resolution scoping feels like a different operation to the existing
O_* flags. And since openat(2) has limited flag space, it seems to be
quite wasteful to clutter it with 5 flags that are all
resolution-related. Arguably O_NOFOLLOW is also a resolution flag but
its entire purpose is to error out if you encounter a trailing
symlink -- not to scope resolution.
* Other systems would be able to reimplement this syscall allowing for
cross-OS standardisation rather than being hidden amongst O_* flags
which may result in it not being used by all the parties that might
want to use it (file servers, web servers, container runtimes, etc).
* It gives us the opportunity to iterate on the O_PATH interface. In
particular, the new @how->upgrade_mask field for fd re-opening is
only possible because we have a clean slate without needing to re-use
the ACC_MODE flag design nor the existing openat(2) @mode semantics.
To this end, we introduce the openat2(2) syscall. It provides all of the
features of openat(2) through the @how->flags argument, but also
also provides a new @how->resolve argument which exposes RESOLVE_* flags
that map to our new LOOKUP_* flags. It also eliminates the long-standing
ugliness of variadic-open(2) by embedding it in a struct.
In order to allow for userspace to lock down their usage of file
descriptor re-opening, openat2(2) has the ability for users to disallow
certain re-opening modes through @how->upgrade_mask. At the moment,
there is no UPGRADE_NOEXEC. The open_how struct is padded to 64 bytes
for future extensions (all of the reserved bits must be zeroed).
[1]: https://github.com/openSUSE/libpathrs
Co-developed-by: Christian Brauner <christian@...uner.io>
Signed-off-by: Aleksa Sarai <cyphar@...har.com>
---
arch/alpha/kernel/syscalls/syscall.tbl | 1 +
arch/arm/tools/syscall.tbl | 1 +
arch/arm64/include/asm/unistd.h | 2 +-
arch/arm64/include/asm/unistd32.h | 2 +
arch/ia64/kernel/syscalls/syscall.tbl | 1 +
arch/m68k/kernel/syscalls/syscall.tbl | 1 +
arch/microblaze/kernel/syscalls/syscall.tbl | 1 +
arch/mips/kernel/syscalls/syscall_n32.tbl | 1 +
arch/mips/kernel/syscalls/syscall_n64.tbl | 1 +
arch/mips/kernel/syscalls/syscall_o32.tbl | 1 +
arch/parisc/kernel/syscalls/syscall.tbl | 1 +
arch/powerpc/kernel/syscalls/syscall.tbl | 1 +
arch/s390/kernel/syscalls/syscall.tbl | 1 +
arch/sh/kernel/syscalls/syscall.tbl | 1 +
arch/sparc/kernel/syscalls/syscall.tbl | 1 +
arch/x86/entry/syscalls/syscall_32.tbl | 1 +
arch/x86/entry/syscalls/syscall_64.tbl | 1 +
arch/xtensa/kernel/syscalls/syscall.tbl | 1 +
fs/open.c | 106 ++++++++++++++++----
include/linux/fcntl.h | 15 ++-
include/linux/fs.h | 4 +-
include/linux/syscalls.h | 17 +++-
include/uapi/asm-generic/unistd.h | 4 +-
include/uapi/linux/fcntl.h | 42 ++++++++
24 files changed, 178 insertions(+), 30 deletions(-)
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index 9e7704e44f6d..cebe813a947f 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -473,3 +473,4 @@
541 common fsconfig sys_fsconfig
542 common fsmount sys_fsmount
543 common fspick sys_fspick
+547 common openat2 sys_openat2
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index aaf479a9e92d..2a0b94e595e7 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -447,3 +447,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+437 common openat2 sys_openat2
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index c9f8dd421c5f..40b8fec7ba55 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -33,7 +33,7 @@
#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5)
#define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)
-#define __NR_compat_syscalls 434
+#define __NR_compat_syscalls 438
#endif
#define __ARCH_WANT_SYS_CLONE
diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index aa995920bd34..df60d417832e 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -875,6 +875,8 @@ __SYSCALL(__NR_fsconfig, sys_fsconfig)
__SYSCALL(__NR_fsmount, sys_fsmount)
#define __NR_fspick 433
__SYSCALL(__NR_fspick, sys_fspick)
+#define __NR_openat2 437
+__SYSCALL(__NR_openat2, sys_openat2)
/*
* Please add new compat syscalls above this comment and update
diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl
index e01df3f2f80d..4da37f0f17fc 100644
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -354,3 +354,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+437 common openat2 sys_openat2
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index 7e3d0734b2f3..323a3695c8a3 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -433,3 +433,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+437 common openat2 sys_openat2
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 26339e417695..8a5b81663387 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -439,3 +439,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+437 common openat2 sys_openat2
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index 0e2dd68ade57..70dfc63d160d 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -372,3 +372,4 @@
431 n32 fsconfig sys_fsconfig
432 n32 fsmount sys_fsmount
433 n32 fspick sys_fspick
+437 n32 openat2 sys_openat2
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index 5eebfa0d155c..1fcad88a326f 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -348,3 +348,4 @@
431 n64 fsconfig sys_fsconfig
432 n64 fsmount sys_fsmount
433 n64 fspick sys_fspick
+437 n64 openat2 sys_openat2
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 3cc1374e02d0..5ef8bdce49ca 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -421,3 +421,4 @@
431 o32 fsconfig sys_fsconfig
432 o32 fsmount sys_fsmount
433 o32 fspick sys_fspick
+437 o32 openat2 sys_openat2 sys_openat2
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index c9e377d59232..176de3591738 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -430,3 +430,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+437 common openat2 sys_openat2
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 103655d84b4b..59591311f8e2 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -515,3 +515,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+437 common openat2 sys_openat2
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index e822b2964a83..36ca509e26c2 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -436,3 +436,4 @@
431 common fsconfig sys_fsconfig sys_fsconfig
432 common fsmount sys_fsmount sys_fsmount
433 common fspick sys_fspick sys_fspick
+437 common openat2 sys_openat2 sys_openat2
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index 016a727d4357..d5ba779f92c2 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -436,3 +436,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+437 common openat2 sys_openat2
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index e047480b1605..d45bebdfdfae 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -479,3 +479,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+437 common openat2 sys_openat2
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index ad968b7bac72..88825c5e631f 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -438,3 +438,4 @@
431 i386 fsconfig sys_fsconfig __ia32_sys_fsconfig
432 i386 fsmount sys_fsmount __ia32_sys_fsmount
433 i386 fspick sys_fspick __ia32_sys_fspick
+437 i386 openat2 sys_openat2 __ia32_sys_openat2
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index b4e6f9e6204a..ebfde1799001 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -355,6 +355,7 @@
431 common fsconfig __x64_sys_fsconfig
432 common fsmount __x64_sys_fsmount
433 common fspick __x64_sys_fspick
+437 common openat2 __x64_sys_openat2
#
# x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index 5fa0ee1c8e00..927a642859a1 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -404,3 +404,4 @@
431 common fsconfig sys_fsconfig
432 common fsmount sys_fsmount
433 common fspick sys_fspick
+437 common openat2 sys_openat2
diff --git a/fs/open.c b/fs/open.c
index bdca45528524..062761136f21 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -928,19 +928,29 @@ struct file *open_with_fake_path(const struct path *path, int flags,
}
EXPORT_SYMBOL(open_with_fake_path);
-static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
+static inline int build_open_flags(const struct open_how *how,
+ struct open_flags *op)
{
+ int flags = how->flags;
int lookup_flags = 0;
+ int opath_mask = 0;
int acc_mode = ACC_MODE(flags);
/*
- * Clear out all open flags we don't know about so that we don't report
- * them in fcntl(F_GETFD) or similar interfaces.
+ * Older syscalls still clear these bits before calling
+ * build_open_flags(), but openat2(2) checks all its arguments.
*/
- flags &= VALID_OPEN_FLAGS;
+ if (flags & ~VALID_OPEN_FLAGS)
+ return -EINVAL;
+ if (how->resolve & ~VALID_RESOLVE_FLAGS)
+ return -EINVAL;
+ if (!(how->flags & (O_PATH | O_CREAT | __O_TMPFILE)) && how->mode != 0)
+ return -EINVAL;
+ if (memchr_inv(how->reserved, 0, sizeof(how->reserved)))
+ return -EINVAL;
if (flags & (O_CREAT | __O_TMPFILE))
- op->mode = (mode & S_IALLUGO) | S_IFREG;
+ op->mode = (how->mode & S_IALLUGO) | S_IFREG;
else
op->mode = 0;
@@ -968,6 +978,14 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
*/
flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
acc_mode = 0;
+
+ /* Allow userspace to restrict the re-opening of O_PATH fds. */
+ if (how->upgrade_mask & ~VALID_UPGRADE_FLAGS)
+ return -EINVAL;
+ if (!(how->upgrade_mask & UPGRADE_NOREAD))
+ opath_mask |= FMODE_PATH_READ;
+ if (!(how->upgrade_mask & UPGRADE_NOWRITE))
+ opath_mask |= FMODE_PATH_WRITE;
}
op->open_flag = flags;
@@ -983,8 +1001,7 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
op->acc_mode = acc_mode;
op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
- /* For O_PATH backwards-compatibility we default to an all-set mask. */
- op->opath_mask = FMODE_PATH_READ | FMODE_PATH_WRITE;
+ op->opath_mask = opath_mask;
if (flags & O_CREAT) {
op->intent |= LOOKUP_CREATE;
@@ -998,6 +1015,18 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
lookup_flags |= LOOKUP_FOLLOW;
if (flags & O_EMPTYPATH)
lookup_flags |= LOOKUP_EMPTY;
+
+ if (how->resolve & RESOLVE_NO_XDEV)
+ lookup_flags |= LOOKUP_NO_XDEV;
+ if (how->resolve & RESOLVE_NO_MAGICLINKS)
+ lookup_flags |= LOOKUP_NO_MAGICLINKS;
+ if (how->resolve & RESOLVE_NO_SYMLINKS)
+ lookup_flags |= LOOKUP_NO_SYMLINKS;
+ if (how->resolve & RESOLVE_BENEATH)
+ lookup_flags |= LOOKUP_BENEATH;
+ if (how->resolve & RESOLVE_IN_ROOT)
+ lookup_flags |= LOOKUP_IN_ROOT;
+
op->lookup_flags = lookup_flags;
return 0;
}
@@ -1016,8 +1045,14 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o
struct file *file_open_name(struct filename *name, int flags, umode_t mode)
{
struct open_flags op;
- int err = build_open_flags(flags, mode, &op);
- return err ? ERR_PTR(err) : do_filp_open(AT_FDCWD, name, &op);
+ struct open_how how = {
+ .flags = flags & VALID_OPEN_FLAGS,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+ int err = build_open_flags(&how, &op);
+ if (err)
+ return ERR_PTR(err);
+ return do_filp_open(AT_FDCWD, name, &op);
}
/**
@@ -1048,17 +1083,22 @@ struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
const char *filename, int flags, umode_t mode)
{
struct open_flags op;
- int err = build_open_flags(flags, mode, &op);
+ struct open_how how = {
+ .flags = flags & VALID_OPEN_FLAGS,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+ int err = build_open_flags(&how, &op);
if (err)
return ERR_PTR(err);
return do_file_open_root(dentry, mnt, filename, &op);
}
EXPORT_SYMBOL(file_open_root);
-long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
+long do_sys_open(int dfd, const char __user *filename,
+ struct open_how *how)
{
struct open_flags op;
- int fd = build_open_flags(flags, mode, &op);
+ int fd = build_open_flags(how, &op);
int empty = 0;
struct filename *tmp;
@@ -1071,7 +1111,7 @@ long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
if (!empty)
op.open_flag &= ~O_EMPTYPATH;
- fd = get_unused_fd_flags(flags);
+ fd = get_unused_fd_flags(how->flags);
if (fd >= 0) {
struct file *f = do_filp_open(dfd, tmp, &op);
if (IS_ERR(f)) {
@@ -1088,19 +1128,35 @@ long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
{
- if (force_o_largefile())
- flags |= O_LARGEFILE;
-
- return do_sys_open(AT_FDCWD, filename, flags, mode);
+ return ksys_open(filename, flags, mode);
}
SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
umode_t, mode)
{
+ struct open_how how = {
+ .flags = flags & VALID_OPEN_FLAGS,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+
+ if (force_o_largefile())
+ how.flags |= O_LARGEFILE;
+
+ return do_sys_open(dfd, filename, &how);
+}
+
+SYSCALL_DEFINE3(openat2, int, dfd, const char __user *, filename,
+ const struct open_how __user *, how)
+{
+ struct open_how tmp;
+
+ if (copy_from_user(&tmp, how, sizeof(tmp)))
+ return -EFAULT;
+
if (force_o_largefile())
- flags |= O_LARGEFILE;
+ tmp.flags |= O_LARGEFILE;
- return do_sys_open(dfd, filename, flags, mode);
+ return do_sys_open(dfd, filename, &tmp);
}
#ifdef CONFIG_COMPAT
@@ -1110,7 +1166,11 @@ SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
*/
COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
{
- return do_sys_open(AT_FDCWD, filename, flags, mode);
+ struct open_how how = {
+ .flags = flags & VALID_OPEN_FLAGS,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+ return do_sys_open(AT_FDCWD, filename, &how);
}
/*
@@ -1119,7 +1179,11 @@ COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t,
*/
COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
{
- return do_sys_open(dfd, filename, flags, mode);
+ struct open_how how = {
+ .flags = flags & VALID_OPEN_FLAGS,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+ return do_sys_open(dfd, filename, &how);
}
#endif
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index 2868ae6c8fc1..f7f378e1f43c 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -4,13 +4,26 @@
#include <uapi/linux/fcntl.h>
-/* list of all valid flags for the open/openat flags argument: */
+/* Should open_how.mode be set for older syscalls wrappers? */
+#define OPENHOW_MODE(flags, mode) \
+ (((flags) & (O_CREAT | __O_TMPFILE)) ? (mode) : 0)
+
+/* List of all valid flags for the open/openat flags argument: */
#define VALID_OPEN_FLAGS \
(O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | \
O_APPEND | O_NDELAY | O_NONBLOCK | O_NDELAY | __O_SYNC | O_DSYNC | \
FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \
O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE | O_EMPTYPATH)
+/* List of all valid flags for the how->upgrade_mask argument: */
+#define VALID_UPGRADE_FLAGS \
+ (UPGRADE_NOWRITE | UPGRADE_NOREAD)
+
+/* List of all valid flags for the how->resolve argument: */
+#define VALID_RESOLVE_FLAGS \
+ (RESOLVE_NO_XDEV | RESOLVE_NO_MAGICLINKS | RESOLVE_NO_SYMLINKS | \
+ RESOLVE_BENEATH | RESOLVE_IN_ROOT)
+
#ifndef force_o_largefile
#define force_o_largefile() (!IS_ENABLED(CONFIG_ARCH_32BIT_OFF_T))
#endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f7df213405ea..a3aede2b3a91 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2515,8 +2515,8 @@ extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
struct file *filp);
extern int vfs_fallocate(struct file *file, int mode, loff_t offset,
loff_t len);
-extern long do_sys_open(int dfd, const char __user *filename, int flags,
- umode_t mode);
+extern long do_sys_open(int dfd, const char __user *filename,
+ struct open_how *how);
extern struct file *file_open_name(struct filename *, int, umode_t);
extern struct file *filp_open(const char *, int, umode_t);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 2bcef4c70183..db141c67c977 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -68,6 +68,7 @@ struct sigaltstack;
struct rseq;
union bpf_attr;
struct io_uring_params;
+struct open_how;
#include <linux/types.h>
#include <linux/aio_abi.h>
@@ -438,6 +439,8 @@ asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user,
asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group);
asmlinkage long sys_openat(int dfd, const char __user *filename, int flags,
umode_t mode);
+asmlinkage long sys_openat2(int dfd, const char __user *filename,
+ const struct open_how *how);
asmlinkage long sys_close(unsigned int fd);
asmlinkage long sys_vhangup(void);
@@ -1369,15 +1372,21 @@ static inline int ksys_close(unsigned int fd)
return __close_fd(current->files, fd);
}
-extern long do_sys_open(int dfd, const char __user *filename, int flags,
- umode_t mode);
+extern long do_sys_open(int dfd, const char __user *filename,
+ struct open_how *how);
static inline long ksys_open(const char __user *filename, int flags,
umode_t mode)
{
+ struct open_how how = {
+ .flags = flags & VALID_OPEN_FLAGS,
+ .mode = OPENHOW_MODE(flags, mode),
+ };
+
if (force_o_largefile())
- flags |= O_LARGEFILE;
- return do_sys_open(AT_FDCWD, filename, flags, mode);
+ how.flags |= O_LARGEFILE;
+
+ return do_sys_open(AT_FDCWD, filename, &how);
}
extern long do_sys_truncate(const char __user *pathname, loff_t length);
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index a87904daf103..e4e8eb7b20c1 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -844,9 +844,11 @@ __SYSCALL(__NR_fsconfig, sys_fsconfig)
__SYSCALL(__NR_fsmount, sys_fsmount)
#define __NR_fspick 433
__SYSCALL(__NR_fspick, sys_fspick)
+#define __NR_openat2 437
+__SYSCALL(__NR_openat2, sys_openat2)
#undef __NR_syscalls
-#define __NR_syscalls 434
+#define __NR_syscalls 438
/*
* 32 bit systems traditionally used different
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index 1d338357df8a..ebfc97b3d8aa 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -93,5 +93,47 @@
#define AT_RECURSIVE 0x8000 /* Apply to the entire subtree */
+/**
+ * Arguments for how openat2(2) should open the target path. If @resolve is
+ * zero, then openat2(2) operates identically to openat(2).
+ *
+ * However, unlike openat(2), unknown bits in @flags result in -EINVAL rather
+ * than being silently ignored. In addition, @mode (or @upgrade_mask) must be
+ * zero unless one of {O_CREAT, O_TMPFILE, O_PATH} are set.
+ *
+ * @flags: O_* flags.
+ * @mode: O_CREAT/O_TMPFILE file mode.
+ * @upgrade_mask: UPGRADE_* flags (to restrict O_PATH re-opening).
+ * @resolve: RESOLVE_* flags.
+ * @reserved: reserved for future extensions, must be zeroed.
+ */
+struct open_how {
+ __u32 flags;
+ union {
+ __u16 mode;
+ __u16 upgrade_mask;
+ };
+ __u16 resolve;
+ __u64 reserved[7]; /* must be zeroed */
+};
+
+/* how->resolve flags for openat2(2). */
+#define RESOLVE_NO_XDEV 0x01 /* Block mount-point crossings
+ (includes bind-mounts). */
+#define RESOLVE_NO_MAGICLINKS 0x02 /* Block traversal through procfs-style
+ "magic-links". */
+#define RESOLVE_NO_SYMLINKS 0x04 /* Block traversal through all symlinks
+ (implies OEXT_NO_MAGICLINKS) */
+#define RESOLVE_BENEATH 0x08 /* Block "lexical" trickery like
+ "..", symlinks, and absolute
+ paths which escape the dirfd. */
+#define RESOLVE_IN_ROOT 0x10 /* Make all jumps to "/" and ".."
+ be scoped inside the dirfd
+ (similar to chroot(2)). */
+
+/* how->upgrade flags for openat2(2). */
+/* First bit is reserved for a future UPGRADE_NOEXEC flag. */
+#define UPGRADE_NOREAD 0x02 /* Block re-opening with MAY_READ. */
+#define UPGRADE_NOWRITE 0x04 /* Block re-opening with MAY_WRITE. */
#endif /* _UAPI_LINUX_FCNTL_H */
--
2.22.0
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