The branch stable/13 has been updated by kib:
URL:
https://cgit.FreeBSD.org/src/commit/?id=824cca5934e522b72d9806cf493c56d030f8ce63
commit 824cca5934e522b72d9806cf493c56d030f8ce63
Author: Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2021-05-06 17:16:53 +0000
Commit: Konstantin Belousov <k...@freebsd.org>
CommitDate: 2021-05-19 03:13:14 +0000
openat(2): add O_EMPTY_PATH
(cherry picked from commit 5e7cdf1817924f8ae0333c0b53c2da32f35b65ea)
---
lib/libc/sys/open.2 | 18 +++++++++++++++++-
sys/kern/vfs_vnops.c | 2 ++
sys/sys/fcntl.h | 3 +++
3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/lib/libc/sys/open.2 b/lib/libc/sys/open.2
index a7806df69daf..5a6f161291f6 100644
--- a/lib/libc/sys/open.2
+++ b/lib/libc/sys/open.2
@@ -28,7 +28,7 @@
.\" @(#)open.2 8.2 (Berkeley) 11/16/93
.\" $FreeBSD$
.\"
-.Dd March 18, 2021
+.Dd May 6, 2021
.Dt OPEN 2
.Os
.Sh NAME
@@ -169,6 +169,7 @@ O_CLOEXEC set FD_CLOEXEC upon open
O_VERIFY verify the contents of the file
O_RESOLVE_BENEATH path resolution must not cross the fd directory
O_PATH record only the target path in the opened descriptor
+O_EMPTY_PATH openat, open file referenced by fd if path is empty
.Ed
.Pp
Opening a file with
@@ -355,6 +356,21 @@ are not allowed.
File opened with the
.Dv O_PATH
flag does not prevent non-forced unmount of the volume it belongs to.
+.Pp
+A file descriptor created with the
+.Dv O_PATH
+flag can be opened into normal (operable) file descriptor by
+specifying it as the
+.Fa fd
+argument to
+.Fn openat
+with empty
+.Fa path
+and flag
+.Dv O_EMPTY_PATH .
+Such an open behaves as if the current path of the file referenced by
+.Fa fd
+is passed, except that the path walk permissions are not checked.
See also the description of
.Dv AT_EMPTY_PATH
flag for
diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index d4396f67a67b..670bc4bf8fcc 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -200,6 +200,8 @@ open2nameif(int fmode, u_int vn_open_flags)
res = ISOPEN | LOCKLEAF;
if ((fmode & O_RESOLVE_BENEATH) != 0)
res |= RBENEATH;
+ if ((fmode & O_EMPTY_PATH) != 0)
+ res |= EMPTYPATH;
if ((vn_open_flags & VN_OPEN_NOAUDIT) == 0)
res |= AUDITVNODE1;
if ((vn_open_flags & VN_OPEN_NOCAPCHECK) != 0)
diff --git a/sys/sys/fcntl.h b/sys/sys/fcntl.h
index 58d46ae26338..8fa52aeacafd 100644
--- a/sys/sys/fcntl.h
+++ b/sys/sys/fcntl.h
@@ -141,6 +141,9 @@ typedef __pid_t pid_t;
#endif
#define O_DSYNC 0x01000000 /* POSIX data sync */
+#if __BSD_VISIBLE
+#define O_EMPTY_PATH 0x02000000
+#endif
/*
* XXX missing O_RSYNC.
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