Commit 66590610 authored by Kees Cook's avatar Kees Cook

fs: Move __scm_install_fd() to __receive_fd()

In preparation for users of the "install a received file" logic outside
of net/ (pidfd and seccomp), relocate and rename __scm_install_fd() from
net/core/scm.c to __receive_fd() in fs/file.c, and provide a wrapper
named receive_fd_user(), as future patches will change the interface
to __receive_fd().

Additionally add a comment to fd_install() as a counterpoint to how
__receive_fd() interacts with fput().

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Dmitry Kadashev <dkadashev@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Ido Schimmel <idosch@idosch.org>
Cc: Ioana Ciornei <ioana.ciornei@nxp.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: netdev@vger.kernel.org
Reviewed-by: default avatarSargun Dhillon <sargun@sargun.me>
Acked-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent c0029de5
......@@ -18,6 +18,7 @@
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
#include <net/sock.h>
unsigned int sysctl_nr_open __read_mostly = 1024*1024;
unsigned int sysctl_nr_open_min = BITS_PER_LONG;
......@@ -613,6 +614,10 @@ void __fd_install(struct files_struct *files, unsigned int fd,
rcu_read_unlock_sched();
}
/*
* This consumes the "file" refcount, so callers should treat it
* as if they had called fput(file).
*/
void fd_install(unsigned int fd, struct file *file)
{
__fd_install(current->files, fd, file);
......@@ -931,6 +936,46 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags)
return err;
}
/**
* __receive_fd() - Install received file into file descriptor table
*
* @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
*
* Installs a received file into the file descriptor table, with appropriate
* checks and count updates. Writes the fd number to userspace.
*
* This helper handles its own reference counting of the incoming
* struct file.
*
* Returns -ve on error.
*/
int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
{
int new_fd;
int error;
error = security_file_receive(file);
if (error)
return error;
new_fd = get_unused_fd_flags(o_flags);
if (new_fd < 0)
return new_fd;
error = put_user(new_fd, ufd);
if (error) {
put_unused_fd(new_fd);
return error;
}
/* Bump the sock usage counts, if any. */
__receive_sock(file);
fd_install(new_fd, get_file(file));
return 0;
}
static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
{
int err = -EBADF;
......
......@@ -91,6 +91,14 @@ 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,
unsigned int o_flags);
static inline int receive_fd_user(struct file *file, int __user *ufd,
unsigned int o_flags)
{
return __receive_fd(file, ufd, o_flags);
}
extern void flush_delayed_fput(void);
extern void __fput_sync(struct file *);
......
......@@ -37,7 +37,6 @@ struct scm_cookie {
#endif
};
int __scm_install_fd(struct file *file, int __user *ufd, unsigned int o_flags);
void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm);
void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm);
int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm);
......
......@@ -298,7 +298,7 @@ void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm)
int err = 0, i;
for (i = 0; i < fdmax; i++) {
err = __scm_install_fd(scm->fp->fp[i], cmsg_data + i, o_flags);
err = receive_fd_user(scm->fp->fp[i], cmsg_data + i, o_flags);
if (err)
break;
}
......
......@@ -280,31 +280,6 @@ void put_cmsg_scm_timestamping(struct msghdr *msg, struct scm_timestamping_inter
}
EXPORT_SYMBOL(put_cmsg_scm_timestamping);
int __scm_install_fd(struct file *file, int __user *ufd, unsigned int o_flags)
{
int new_fd;
int error;
error = security_file_receive(file);
if (error)
return error;
new_fd = get_unused_fd_flags(o_flags);
if (new_fd < 0)
return new_fd;
error = put_user(new_fd, ufd);
if (error) {
put_unused_fd(new_fd);
return error;
}
/* Bump the sock usage counts, if any. */
__receive_sock(file);
fd_install(new_fd, get_file(file));
return 0;
}
static int scm_max_fds(struct msghdr *msg)
{
if (msg->msg_controllen <= sizeof(struct cmsghdr))
......@@ -331,7 +306,7 @@ void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
}
for (i = 0; i < fdmax; i++) {
err = __scm_install_fd(scm->fp->fp[i], cmsg_data + i, o_flags);
err = receive_fd_user(scm->fp->fp[i], cmsg_data + i, o_flags);
if (err)
break;
}
......
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