From: Ameer Hamza <ahamza@ixsystems.com>
To: viro@zeniv.linux.org.uk, jlayton@kernel.org,
chuck.lever@oracle.com, arnd@arndb.de, guoren@kernel.org,
palmer@rivosinc.com, f.fainelli@gmail.com, slark_xiao@163.com
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org, ahamza@ixsystems.com,
awalker@ixsystems.com
Subject: [PATCH] Add new open(2) flag - O_EMPTY_PATH
Date: Wed, 28 Dec 2022 21:02:49 +0500 [thread overview]
Message-ID: <20221228160249.428399-1-ahamza@ixsystems.com> (raw)
This patch adds a new flag O_EMPTY_PATH that allows openat and open
system calls to open a file referenced by fd if the path is empty,
and it is very similar to the FreeBSD O_EMPTY_PATH flag. This can be
beneficial in some cases since it would avoid having to grant /proc
access to things like samba containers for reopening files to change
flags in a race-free way.
Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>
---
fs/fcntl.c | 2 +-
fs/namei.c | 4 ++--
fs/open.c | 2 +-
include/linux/fcntl.h | 2 +-
include/uapi/asm-generic/fcntl.h | 4 ++++
tools/include/uapi/asm-generic/fcntl.h | 4 ++++
6 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 146c9ab0cd4b..7aac650e16e2 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -1027,7 +1027,7 @@ static int __init fcntl_init(void)
* Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
* is defined as O_NONBLOCK on some platforms and not on others.
*/
- BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ !=
+ BUILD_BUG_ON(22 - 1 /* for O_RDONLY being 0 */ !=
HWEIGHT32(
(VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) |
__FMODE_EXEC | __FMODE_NONOTIFY));
diff --git a/fs/namei.c b/fs/namei.c
index 309ae6fc8c99..2b2735af6d03 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -192,7 +192,7 @@ getname_flags(const char __user *filename, int flags, int *empty)
if (unlikely(!len)) {
if (empty)
*empty = 1;
- if (!(flags & LOOKUP_EMPTY)) {
+ if (!(flags & (LOOKUP_EMPTY | O_EMPTY_PATH))) {
putname(result);
return ERR_PTR(-ENOENT);
}
@@ -2347,7 +2347,7 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED)
return ERR_PTR(-EAGAIN);
- if (!*s)
+ if (!*s && unlikely(!(flags & O_EMPTY_PATH)))
flags &= ~LOOKUP_RCU;
if (flags & LOOKUP_RCU)
rcu_read_lock();
diff --git a/fs/open.c b/fs/open.c
index 82c1a28b3308..b4ec054a418f 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1301,7 +1301,7 @@ static long do_sys_openat2(int dfd, const char __user *filename,
if (fd)
return fd;
- tmp = getname(filename);
+ tmp = getname_flags(filename, how->flags & O_EMPTY_PATH, NULL);
if (IS_ERR(tmp))
return PTR_ERR(tmp);
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index a332e79b3207..bf8467bb0bd2 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -10,7 +10,7 @@
(O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | \
O_APPEND | O_NDELAY | O_NONBLOCK | __O_SYNC | O_DSYNC | \
FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \
- O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE)
+ O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE | O_EMPTY_PATH)
/* List of all valid flags for the how->resolve argument: */
#define VALID_RESOLVE_FLAGS \
diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h
index 1ecdb911add8..a03f4275517b 100644
--- a/include/uapi/asm-generic/fcntl.h
+++ b/include/uapi/asm-generic/fcntl.h
@@ -89,6 +89,10 @@
#define __O_TMPFILE 020000000
#endif
+#ifndef O_EMPTY_PATH
+#define O_EMPTY_PATH 040000000
+#endif
+
/* a horrid kludge trying to make sure that this will fail on old kernels */
#define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
#define O_TMPFILE_MASK (__O_TMPFILE | O_DIRECTORY | O_CREAT)
diff --git a/tools/include/uapi/asm-generic/fcntl.h b/tools/include/uapi/asm-generic/fcntl.h
index b02c8e0f4057..f32a81604296 100644
--- a/tools/include/uapi/asm-generic/fcntl.h
+++ b/tools/include/uapi/asm-generic/fcntl.h
@@ -89,6 +89,10 @@
#define __O_TMPFILE 020000000
#endif
+#ifndef O_EMPTY_PATH
+#define O_EMPTY_PATH 040000000
+#endif
+
/* a horrid kludge trying to make sure that this will fail on old kernels */
#define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
#define O_TMPFILE_MASK (__O_TMPFILE | O_DIRECTORY | O_CREAT)
--
2.25.1
next reply other threads:[~2022-12-28 16:05 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-28 16:02 Ameer Hamza [this message]
2022-12-31 0:15 ` [PATCH] Add new open(2) flag - O_EMPTY_PATH kernel test robot
2022-12-31 23:56 ` [PATCH v2] " Ameer Hamza
2023-01-01 11:16 ` kernel test robot
2023-01-01 15:37 ` [PATCH v3] " Ameer Hamza
2023-01-02 14:01 ` [PATCH v2] " David Laight
2023-01-02 14:35 ` Ameer Hamza
2023-01-06 9:21 ` David Laight
2023-01-06 13:06 ` [PATCH] " Christian Brauner
2023-04-19 1:15 ` Ameer Hamza
[not found] ` <7454A798-1277-411A-853C-635B33439029@gmail.com>
2023-04-19 9:18 ` Christian Brauner
2023-04-19 21:29 ` David Laight
2023-04-26 13:10 ` Andrew Walker
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