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Date: Fri, 26 Apr 2024 16:33:09 +0300
From: Stas Sergeev <stsp2@...dex.ru>
To: linux-kernel@...r.kernel.org
Cc: Stas Sergeev <stsp2@...dex.ru>,
Stefan Metzmacher <metze@...ba.org>,
Eric Biederman <ebiederm@...ssion.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Andy Lutomirski <luto@...nel.org>,
Christian Brauner <brauner@...nel.org>,
Jan Kara <jack@...e.cz>,
Jeff Layton <jlayton@...nel.org>,
Chuck Lever <chuck.lever@...cle.com>,
Alexander Aring <alex.aring@...il.com>,
David Laight <David.Laight@...LAB.COM>,
linux-fsdevel@...r.kernel.org,
linux-api@...r.kernel.org,
Paolo Bonzini <pbonzini@...hat.com>,
Christian Göttsche <cgzones@...glemail.com>,
Arnd Bergmann <arnd@...db.de>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Jens Axboe <axboe@...nel.dk>,
Kuniyuki Iwashima <kuniyu@...zon.com>,
Pavel Begunkov <asml.silence@...il.com>,
linux-arch@...r.kernel.org,
netdev@...r.kernel.org
Subject: [PATCH v5 2/3] open: add O_CRED_ALLOW flag
This flag prevents an fd from being passed via unix socket, and
makes it to be always closed on exec().
It is needed for the subsequent OA2_CRED_INHERIT addition, to work
as an "opt-in" for the new cred-inherit functionality. Without using
O_CRED_ALLOW when opening dir fd, it won't be possible to use
OA2_CRED_INHERIT on that dir fd.
Signed-off-by: Stas Sergeev <stsp2@...dex.ru>
CC: Eric Biederman <ebiederm@...ssion.com>
CC: Alexander Viro <viro@...iv.linux.org.uk>
CC: Christian Brauner <brauner@...nel.org>
CC: Jan Kara <jack@...e.cz>
CC: Andy Lutomirski <luto@...nel.org>
CC: David Laight <David.Laight@...LAB.COM>
CC: Arnd Bergmann <arnd@...db.de>
CC: "David S. Miller" <davem@...emloft.net>
CC: Eric Dumazet <edumazet@...gle.com>
CC: Jakub Kicinski <kuba@...nel.org>
CC: Paolo Abeni <pabeni@...hat.com>
CC: Jens Axboe <axboe@...nel.dk>
CC: Kuniyuki Iwashima <kuniyu@...zon.com>
CC: Pavel Begunkov <asml.silence@...il.com>
CC: linux-arch@...r.kernel.org
CC: netdev@...r.kernel.org
CC: linux-fsdevel@...r.kernel.org
CC: linux-kernel@...r.kernel.org
CC: linux-api@...r.kernel.org
---
fs/fcntl.c | 2 +-
fs/file.c | 15 ++++++++-------
include/linux/fcntl.h | 2 +-
include/uapi/asm-generic/fcntl.h | 4 ++++
net/core/scm.c | 5 +++++
5 files changed, 19 insertions(+), 9 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 54cc85d3338e..78c96b1293c2 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -1039,7 +1039,7 @@ 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/file.c b/fs/file.c
index 3b683b9101d8..2a09d5276676 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -827,22 +827,23 @@ void do_close_on_exec(struct files_struct *files)
/* exec unshares first */
spin_lock(&files->file_lock);
for (i = 0; ; i++) {
+ int j;
unsigned long set;
unsigned fd = i * BITS_PER_LONG;
fdt = files_fdtable(files);
if (fd >= fdt->max_fds)
break;
set = fdt->close_on_exec[i];
- if (!set)
- continue;
fdt->close_on_exec[i] = 0;
- for ( ; set ; fd++, set >>= 1) {
- struct file *file;
- if (!(set & 1))
- continue;
- file = fdt->fd[fd];
+ for (j = 0; j < BITS_PER_LONG; j++, fd++, set >>= 1) {
+ struct file *file = fdt->fd[fd];
if (!file)
continue;
+ /* Close all cred-allow files. */
+ if (file->f_flags & O_CRED_ALLOW)
+ set |= 1;
+ if (!(set & 1))
+ continue;
rcu_assign_pointer(fdt->fd[fd], NULL);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index a332e79b3207..e074ee9c1e36 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_CRED_ALLOW)
/* 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 80f37a0d40d7..ee8c2267c516 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_CRED_ALLOW
+#define O_CRED_ALLOW 040000000
+#endif
+
/* a horrid kludge trying to make sure that this will fail on old kernels */
#define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
diff --git a/net/core/scm.c b/net/core/scm.c
index 9cd4b0a01cd6..f54fb0ee9727 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -111,6 +111,11 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
fput(file);
return -EINVAL;
}
+ /* don't allow files with creds */
+ if (file->f_flags & O_CRED_ALLOW) {
+ fput(file);
+ return -EPERM;
+ }
if (unix_get_socket(file))
fpl->count_unix++;
--
2.44.0
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