From: Kees Cook <keescook@chromium.org>
To: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>,
Sargun Dhillon <sargun@sargun.me>,
Christian Brauner <christian@brauner.io>,
Tycho Andersen <tycho@tycho.ws>,
David Laight <David.Laight@ACULAB.COM>,
Christoph Hellwig <hch@lst.de>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Aleksa Sarai <cyphar@cyphar.com>,
Matt Denton <mpdenton@google.com>, Jann Horn <jannh@google.com>,
Chris Palmer <palmer@google.com>,
Robert Sesek <rsesek@google.com>,
Giuseppe Scrivano <gscrivan@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andy Lutomirski <luto@amacapital.net>,
Will Drewry <wad@chromium.org>, Shuah Khan <shuah@kernel.org>,
netdev@vger.kernel.org, containers@lists.linux-foundation.org,
linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: [PATCH v6 5/7] fs: Expand __receive_fd() to accept existing fd
Date: Mon, 6 Jul 2020 13:17:18 -0700 [thread overview]
Message-ID: <20200706201720.3482959-6-keescook@chromium.org> (raw)
In-Reply-To: <20200706201720.3482959-1-keescook@chromium.org>
Expand __receive_fd() with support for replace_fd() for the coming seccomp
"addfd" ioctl(). Add new wrapper receive_fd_replace() for the new behavior
and update existing wrappers to retain old behavior.
Thanks to Colin Ian King <colin.king@canonical.com> for pointing out an
uninitialized variable exposure in an earlier version of this patch.
Reviewed-by: Sargun Dhillon <sargun@sargun.me>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/file.c | 24 ++++++++++++++++++------
include/linux/file.h | 10 +++++++---
2 files changed, 25 insertions(+), 9 deletions(-)
diff --git a/fs/file.c b/fs/file.c
index 0efdcf413210..11313ff36802 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -937,6 +937,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags)
/**
* __receive_fd() - Install received file into file descriptor table
*
+ * @fd: fd to install into (if negative, a new fd will be allocated)
* @file: struct file that was received from another process
* @ufd: __user pointer to write new fd number to
* @o_flags: the O_* flags to apply to the new fd entry
@@ -950,7 +951,7 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags)
*
* Returns newly install fd or -ve on error.
*/
-int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
+int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags)
{
struct socket *sock;
int new_fd;
@@ -960,18 +961,30 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
if (error)
return error;
- new_fd = get_unused_fd_flags(o_flags);
- if (new_fd < 0)
- return new_fd;
+ if (fd < 0) {
+ new_fd = get_unused_fd_flags(o_flags);
+ if (new_fd < 0)
+ return new_fd;
+ } else
+ new_fd = fd;
if (ufd) {
error = put_user(new_fd, ufd);
if (error) {
- put_unused_fd(new_fd);
+ if (fd < 0)
+ put_unused_fd(new_fd);
return error;
}
}
+ if (fd < 0)
+ fd_install(new_fd, get_file(file));
+ else {
+ error = replace_fd(new_fd, file, o_flags);
+ if (error)
+ return error;
+ }
+
/*
* Bump the usage count and install the file. The resulting value of
* "error" is ignored here since we only need to take action when
@@ -982,7 +995,6 @@ int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
sock_update_netprioidx(&sock->sk->sk_cgrp_data);
sock_update_classid(&sock->sk->sk_cgrp_data);
}
- fd_install(new_fd, get_file(file));
return new_fd;
}
diff --git a/include/linux/file.h b/include/linux/file.h
index d9fee9f5c8da..225982792fa2 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -92,18 +92,22 @@ extern void put_unused_fd(unsigned int fd);
extern void fd_install(unsigned int fd, struct file *file);
-extern int __receive_fd(struct file *file, int __user *ufd,
+extern int __receive_fd(int fd, struct file *file, int __user *ufd,
unsigned int o_flags);
static inline int receive_fd_user(struct file *file, int __user *ufd,
unsigned int o_flags)
{
if (ufd == NULL)
return -EFAULT;
- return __receive_fd(file, ufd, o_flags);
+ return __receive_fd(-1, file, ufd, o_flags);
}
static inline int receive_fd(struct file *file, unsigned int o_flags)
{
- return __receive_fd(file, NULL, o_flags);
+ return __receive_fd(-1, file, NULL, o_flags);
+}
+static inline int receive_fd_replace(int fd, struct file *file, unsigned int o_flags)
+{
+ return __receive_fd(fd, file, NULL, o_flags);
}
extern void flush_delayed_fput(void);
--
2.25.1
next prev parent reply other threads:[~2020-07-06 20:18 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-06 20:17 [PATCH v6 0/7] Add seccomp notifier ioctl that enables adding fds Kees Cook
2020-07-06 20:17 ` [PATCH v6 1/7] net/scm: Regularize compat handling of scm_detach_fds() Kees Cook
2020-07-07 11:41 ` Christian Brauner
2020-07-08 23:46 ` Kees Cook
2020-07-06 20:17 ` [PATCH v6 2/7] fs: Move __scm_install_fd() to __receive_fd() Kees Cook
2020-07-07 6:49 ` Christoph Hellwig
2020-07-07 11:45 ` Christian Brauner
2020-07-06 20:17 ` [PATCH v6 3/7] fs: Add receive_fd() wrapper for __receive_fd() Kees Cook
2020-07-07 6:49 ` Christoph Hellwig
2020-07-07 11:49 ` Christian Brauner
2020-07-08 23:48 ` Kees Cook
2020-07-06 20:17 ` [PATCH v6 4/7] pidfd: Replace open-coded partial receive_fd() Kees Cook
2020-07-07 12:22 ` Christian Brauner
2020-07-08 23:49 ` Kees Cook
2020-07-09 6:35 ` Kees Cook
2020-07-09 12:54 ` Christian Brauner
2020-07-06 20:17 ` Kees Cook [this message]
2020-07-07 12:38 ` [PATCH v6 5/7] fs: Expand __receive_fd() to accept existing fd Christian Brauner
2020-07-08 23:52 ` Kees Cook
2020-07-06 20:17 ` [PATCH v6 6/7] seccomp: Introduce addfd ioctl to seccomp user notifier Kees Cook
2020-07-07 13:30 ` Christian Brauner
2020-07-09 6:12 ` Kees Cook
2020-07-09 13:08 ` Christian Brauner
2020-07-09 6:17 ` [PATCH v6.1 " Kees Cook
2020-07-09 6:22 ` Kees Cook
2020-07-06 20:17 ` [PATCH v6 7/7] selftests/seccomp: Test SECCOMP_IOCTL_NOTIF_ADDFD Kees Cook
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