[PATCH] sctp: Add peeloff-flags socket option

Neil Horman
2017-06-29T18:13:40Z

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@tuxdriver.com>
CC: Alexander Viro <viro@zeniv.linux.org.uk>
CC: Vlad Yasevich <vyasevich@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: Andreas Steinmetz <ast@domdv.de>
CC: Marcelo Ricardo Leitner <marcelo.leitner@gmail.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;

- 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));
+
+ if (flags & SOCK_NONBLOCK)
+ (*newfile)->f_flags |= O_NONBLOCK;
+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)
+ fput(newfile);
put_unused_fd(retval);
return -EFAULT;
}
- peeloff.sd = retval;
+
if (copy_to_user(optval, &peeloff, len)) {
- fput(newfile);
+ if (newfile)
+ 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