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Message-ID: <20170629190405.GL18138@localhost.localdomain>
Date: Thu, 29 Jun 2017 16:04:05 -0300
From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To: Neil Horman <nhorman@...driver.com>
Cc: linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
Vlad Yasevich <vyasevich@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Andreas Steinmetz <ast@...dv.de>
Subject: Re: [PATCH] sctp: Add peeloff-flags socket option
On Thu, Jun 29, 2017 at 02:13:40PM -0400, Neil Horman wrote:
> Based on a request raised on the sctp devel list, there is a need to
> augment the sctp_peeloff operation while specifying the O_CLOEXEC and
> O_NONBLOCK flags (simmilar to the socket syscall). Since modifying the
> SCTP_SOCKOPT_PEELOFF socket option would break user space ABI for existing
> programs, this patch creates a new socket option
> SCTP_SOCKOPT_PEELOFF_FLAGS, which accepts a third flags parameter to
> allow atomic assignment of the socket descriptor flags.
>
> Tested successfully by myself and the requestor
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>
> CC: Alexander Viro <viro@...iv.linux.org.uk>
> CC: Vlad Yasevich <vyasevich@...il.com>
> CC: "David S. Miller" <davem@...emloft.net>
> CC: Andreas Steinmetz <ast@...dv.de>
> CC: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> ---
> fs/file.c | 1 +
> include/uapi/linux/sctp.h | 6 ++++
> net/sctp/socket.c | 92 ++++++++++++++++++++++++++++++++++++++---------
> 3 files changed, 83 insertions(+), 16 deletions(-)
>
> diff --git a/fs/file.c b/fs/file.c
> index 1c2972e..a4521da 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -807,6 +807,7 @@ void set_close_on_exec(unsigned int fd, int flag)
> __clear_close_on_exec(fd, fdt);
> spin_unlock(&files->file_lock);
> }
> +EXPORT_SYMBOL(set_close_on_exec);
>
> bool get_close_on_exec(unsigned int fd)
> {
> diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> index ced9d8b..6217ff8 100644
> --- a/include/uapi/linux/sctp.h
> +++ b/include/uapi/linux/sctp.h
> @@ -121,6 +121,7 @@ typedef __s32 sctp_assoc_t;
> #define SCTP_RESET_STREAMS 119
> #define SCTP_RESET_ASSOC 120
> #define SCTP_ADD_STREAMS 121
> +#define SCTP_SOCKOPT_PEELOFF_FLAGS 122
>
> /* PR-SCTP policies */
> #define SCTP_PR_SCTP_NONE 0x0000
> @@ -978,6 +979,11 @@ typedef struct {
> int sd;
> } sctp_peeloff_arg_t;
>
> +typedef struct {
> + sctp_peeloff_arg_t p_arg;
> + unsigned flags;
> +} sctp_peeloff_flags_arg_t;
> +
> /*
> * Peer Address Thresholds socket option
> */
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 7b6e20e..7341053 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -4933,20 +4933,12 @@ int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp)
> }
> EXPORT_SYMBOL(sctp_do_peeloff);
>
> -static int sctp_getsockopt_peeloff(struct sock *sk, int len, char __user *optval, int __user *optlen)
> +static int sctp_getsockopt_peeloff_common(struct sock *sk, sctp_peeloff_arg_t *peeloff, struct file **newfile, unsigned flags)
> {
> - sctp_peeloff_arg_t peeloff;
> struct socket *newsock;
> - struct file *newfile;
> int retval = 0;
^^^ this initialization is not needed anymore
as the line after it is always assigning it.
>
> - if (len < sizeof(sctp_peeloff_arg_t))
> - return -EINVAL;
> - len = sizeof(sctp_peeloff_arg_t);
> - if (copy_from_user(&peeloff, optval, len))
> - return -EFAULT;
> -
> - retval = sctp_do_peeloff(sk, peeloff.associd, &newsock);
> + retval = sctp_do_peeloff(sk, peeloff->associd, &newsock);
> if (retval < 0)
> goto out;
>
> @@ -4957,25 +4949,90 @@ static int sctp_getsockopt_peeloff(struct sock *sk, int len, char __user *optval
> goto out;
> }
>
> - newfile = sock_alloc_file(newsock, 0, NULL);
> - if (IS_ERR(newfile)) {
> + *newfile = sock_alloc_file(newsock, 0, NULL);
> + if (IS_ERR(*newfile)) {
> put_unused_fd(retval);
> sock_release(newsock);
> - return PTR_ERR(newfile);
> + retval = PTR_ERR(*newfile);
> + *newfile = NULL;
> + return retval;
> }
>
> pr_debug("%s: sk:%p, newsk:%p, sd:%d\n", __func__, sk, newsock->sk,
> retval);
> +
> + peeloff->sd = retval;
> +
> + set_close_on_exec(peeloff->sd, !!(flags & SOCK_CLOEXEC));
You can avoid this call (and the export) if you pass flags &
SOCK_CLOEXEC to get_unused_fd_flags(), which currently uses flags=0.
> +
> + if (flags & SOCK_NONBLOCK)
> + (*newfile)->f_flags |= O_NONBLOCK;
and also to sock_alloc_file().
> +out:
> + return retval;
> +}
> +
> +static int sctp_getsockopt_peeloff(struct sock *sk, int len, char __user *optval, int __user *optlen)
> +{
> + sctp_peeloff_arg_t peeloff;
> + struct file *newfile = NULL;
> + int retval = 0;
> +
> + if (len < sizeof(sctp_peeloff_arg_t))
> + return -EINVAL;
> + len = sizeof(sctp_peeloff_arg_t);
> + if (copy_from_user(&peeloff, optval, len))
> + return -EFAULT;
> +
> + retval = sctp_getsockopt_peeloff_common(sk, &peeloff, &newfile, 0);
> + if (retval < 0)
^^
> + goto out;
>
> /* Return the fd mapped to the new socket. */
> if (put_user(len, optlen)) {
> - fput(newfile);
> + if (newfile)
I don't think you need the if() here because for the file to not be
there, retval above will be negative and this part won't be called.
> + fput(newfile);
> put_unused_fd(retval);
> return -EFAULT;
> }
> - peeloff.sd = retval;
> +
> if (copy_to_user(optval, &peeloff, len)) {
> - fput(newfile);
> + if (newfile)
Same here and on sctp_getsockopt_peeloff_flags() below.
Marcelo
> + fput(newfile);
> + put_unused_fd(retval);
> + return -EFAULT;
> + }
> + fd_install(retval, newfile);
> +out:
> + return retval;
> +}
> +
> +static int sctp_getsockopt_peeloff_flags(struct sock *sk, int len, char __user *optval, int __user *optlen)
> +{
> + sctp_peeloff_flags_arg_t peeloff;
> + struct file *newfile = NULL;
> + int retval = 0;
> +
> + if (len < sizeof(sctp_peeloff_flags_arg_t))
> + return -EINVAL;
> + len = sizeof(sctp_peeloff_flags_arg_t);
> + if (copy_from_user(&peeloff, optval, len))
> + return -EFAULT;
> +
> + retval = sctp_getsockopt_peeloff_common(sk, &peeloff.p_arg, &newfile, peeloff.flags);
> + if (retval < 0)
> + goto out;
> +
> + /* Return the fd mapped to the new socket. */
> + if (put_user(len, optlen)) {
> + if (newfile)
> + fput(newfile);
> + put_unused_fd(retval);
> + return -EFAULT;
> + }
> +
> + if (copy_to_user(optval, &peeloff, len)) {
> + if (newfile)
> + fput(newfile);
> put_unused_fd(retval);
> return -EFAULT;
> }
> @@ -6758,6 +6815,9 @@ static int sctp_getsockopt(struct sock *sk, int level, int optname,
> case SCTP_SOCKOPT_PEELOFF:
> retval = sctp_getsockopt_peeloff(sk, len, optval, optlen);
> break;
> + case SCTP_SOCKOPT_PEELOFF_FLAGS:
> + retval = sctp_getsockopt_peeloff_flags(sk, len, optval, optlen);
> + break;
> case SCTP_PEER_ADDR_PARAMS:
> retval = sctp_getsockopt_peer_addr_params(sk, len, optval,
> optlen);
> --
> 2.9.4
>
> --
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