Commit 66590610 authored by Kees Cook's avatar Kees Cook
Browse files

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

fs/file.c

+45 −0
Original line number Diff line number Diff line
@@ -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 @@ out_unlock: 
	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;

include/linux/file.h

+8 −0
Original line number Diff line number Diff line
@@ -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 *);

include/net/scm.h

+0 −1
Original line number Diff line number Diff line
@@ -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);

net/compat.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

	}

net/core/scm.c

+1 −26
Original line number Diff line number Diff line
@@ -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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