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* [PATCH 3/3] make sock_alloc_file() do sock_release() on failures
@ 2017-12-05 23:29 Al Viro
  2017-12-05 23:41 ` David Miller
  0 siblings, 1 reply; 4+ messages in thread
From: Al Viro @ 2017-12-05 23:29 UTC (permalink / raw)
  To: netdev

This changes calling conventions (and simplifies the hell out
the callers).  New rules: once struct socket had been passed
to sock_alloc_file(), it's been consumed either by struct file
or by sock_release() done by sock_alloc_file().  Either way
the caller should not do sock_release() after that point.

Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 drivers/staging/lustre/lnet/lnet/lib-socket.c |  8 ++------
 net/9p/trans_fd.c                             |  1 -
 net/kcm/kcmsock.c                             |  7 +------
 net/sctp/socket.c                             |  1 -
 net/socket.c                                  | 25 ++++++++-----------------
 5 files changed, 11 insertions(+), 31 deletions(-)

diff --git a/drivers/staging/lustre/lnet/lnet/lib-socket.c b/drivers/staging/lustre/lnet/lnet/lib-socket.c
index 539a26444f31..7d49d4865298 100644
--- a/drivers/staging/lustre/lnet/lnet/lib-socket.c
+++ b/drivers/staging/lustre/lnet/lnet/lib-socket.c
@@ -71,16 +71,12 @@ lnet_sock_ioctl(int cmd, unsigned long arg)
 	}
 
 	sock_filp = sock_alloc_file(sock, 0, NULL);
-	if (IS_ERR(sock_filp)) {
-		sock_release(sock);
-		rc = PTR_ERR(sock_filp);
-		goto out;
-	}
+	if (IS_ERR(sock_filp))
+		return PTR_ERR(sock_filp);
 
 	rc = kernel_sock_unlocked_ioctl(sock_filp, cmd, arg);
 
 	fput(sock_filp);
-out:
 	return rc;
 }
 
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index 985046ae4231..80f5c79053a4 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -839,7 +839,6 @@ static int p9_socket_open(struct p9_client *client, struct socket *csocket)
 	if (IS_ERR(file)) {
 		pr_err("%s (%d): failed to map fd\n",
 		       __func__, task_pid_nr(current));
-		sock_release(csocket);
 		kfree(p);
 		return PTR_ERR(file);
 	}
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index c5fa634e63ca..d4e98f20fc2a 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1629,7 +1629,6 @@ static struct file *kcm_clone(struct socket *osock)
 {
 	struct socket *newsock;
 	struct sock *newsk;
-	struct file *file;
 
 	newsock = sock_alloc();
 	if (!newsock)
@@ -1649,11 +1648,7 @@ static struct file *kcm_clone(struct socket *osock)
 	sock_init_data(newsock, newsk);
 	init_kcm_sock(kcm_sk(newsk), kcm_sk(osock->sk)->mux);
 
-	file = sock_alloc_file(newsock, 0, osock->sk->sk_prot_creator->name);
-	if (IS_ERR(file))
-		sock_release(newsock);
-
-	return file;
+	return sock_alloc_file(newsock, 0, osock->sk->sk_prot_creator->name);
 }
 
 static int kcm_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 3204a9b29407..8bb5163d6331 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -5080,7 +5080,6 @@ static int sctp_getsockopt_peeloff_common(struct sock *sk, sctp_peeloff_arg_t *p
 	*newfile = sock_alloc_file(newsock, 0, NULL);
 	if (IS_ERR(*newfile)) {
 		put_unused_fd(retval);
-		sock_release(newsock);
 		retval = PTR_ERR(*newfile);
 		*newfile = NULL;
 		return retval;
diff --git a/net/socket.c b/net/socket.c
index 2df83c0bfde9..05f361faec45 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -406,8 +406,10 @@ struct file *sock_alloc_file(struct socket *sock, int flags, const char *dname)
 		name.len = strlen(name.name);
 	}
 	path.dentry = d_alloc_pseudo(sock_mnt->mnt_sb, &name);
-	if (unlikely(!path.dentry))
+	if (unlikely(!path.dentry)) {
+		sock_release(sock);
 		return ERR_PTR(-ENOMEM);
+	}
 	path.mnt = mntget(sock_mnt);
 
 	d_instantiate(path.dentry, SOCK_INODE(sock));
@@ -415,9 +417,11 @@ struct file *sock_alloc_file(struct socket *sock, int flags, const char *dname)
 	file = alloc_file(&path, FMODE_READ | FMODE_WRITE,
 		  &socket_file_ops);
 	if (IS_ERR(file)) {
-		/* drop dentry, keep inode */
+		/* drop dentry, keep inode for a bit */
 		ihold(d_inode(path.dentry));
 		path_put(&path);
+		/* ... and now kill it properly */
+		sock_release(sock);
 		return file;
 	}
 
@@ -1330,19 +1334,9 @@ SYSCALL_DEFINE3(socket, int, family, int, type, int, protocol)
 
 	retval = sock_create(family, type, protocol, &sock);
 	if (retval < 0)
-		goto out;
-
-	retval = sock_map_fd(sock, flags & (O_CLOEXEC | O_NONBLOCK));
-	if (retval < 0)
-		goto out_release;
-
-out:
-	/* It may be already another descriptor 8) Not kernel problem. */
-	return retval;
+		return retval;
 
-out_release:
-	sock_release(sock);
-	return retval;
+	return sock_map_fd(sock, flags & (O_CLOEXEC | O_NONBLOCK));
 }
 
 /*
@@ -1412,7 +1406,6 @@ SYSCALL_DEFINE4(socketpair, int, family, int, type, int, protocol,
 	newfile1 = sock_alloc_file(sock1, flags, NULL);
 	if (IS_ERR(newfile1)) {
 		err = PTR_ERR(newfile1);
-		sock_release(sock1);
 		sock_release(sock2);
 		goto out;
 	}
@@ -1420,7 +1413,6 @@ SYSCALL_DEFINE4(socketpair, int, family, int, type, int, protocol,
 	newfile2 = sock_alloc_file(sock2, flags, NULL);
 	if (IS_ERR(newfile2)) {
 		err = PTR_ERR(newfile2);
-		sock_release(sock2);
 		fput(newfile1);
 		goto out;
 	}
@@ -1549,7 +1541,6 @@ SYSCALL_DEFINE4(accept4, int, fd, struct sockaddr __user *, upeer_sockaddr,
 	if (IS_ERR(newfile)) {
 		err = PTR_ERR(newfile);
 		put_unused_fd(newfd);
-		sock_release(newsock);
 		goto out_put;
 	}
 
-- 
2.11.0

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* [RFC][PATCHES] sock_alloc_file() cleanups and fixes
@ 2017-12-01  0:20 Al Viro
  2017-12-01  0:23 ` [PATCH 3/3] make sock_alloc_file() do sock_release() on failures Al Viro
  0 siblings, 1 reply; 4+ messages in thread
From: Al Viro @ 2017-12-01  0:20 UTC (permalink / raw)
  To: netdev; +Cc: Al Viro

	Almost all sock_alloc_file() callers want sock_release()
in case of failure.  Currently it consumes socket on success
(it will be destroyed on final fput() of resulting file) and
leaves it alone on failure.  Making it consume socket in all
cases makes for simpler life in callers.

	There are 3 exceptions:

* sock_map_fd() calls sock_alloc_file(), but doesn't do sock_release()
  in case of failure.  Its caller (sys_socket()) does, though, and it
  does get considerably simpler with sock_alloc_file() doing the cleanup
  in case of failure.

* sys_socketpair().  Handling of sock_alloc_file() failures is complicated
  by attempts to share bits and pieces of failure exits between various
  points of failure in there.  Reordering things a bit (reserving descriptors
  and copying them to userland before doing anything else) makes for simpler
  handling of failure exits and after such massage we get the situation
  when failure of sock_alloc_file() is immediately followed by sock_release().

* kcm_clone().  Badly broken in several respects - sk_alloc() failure ends
  up with double-free of struct socket (we do fput(), then sock_release())
  and copy_to_user() failure uses sys_close() to undo fd_install(), which
  is something we should never do.  Descriptor table might be shared and
  fd_install() should only be done past the last possible failure point.
  Fixing all of that is simple - we just need to move allocation of
  descriptor and fd_install() into the caller (before and after the call of
  kcm_clone(), resp.) and untangle the failure exits.  Makes for much simpler
  calling conventions for kcm_clone(), while we are at it, and as a side
  effect we get "sock_release() in case of sock_alloc_file() failure" for
  that one as well.

	The patch series (in followups to this mail and in
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git#work.net) does
the following:
	1) massage sys_socketpair() (should be a pure cleanup)
	2) fix and clean up kcm_clone() (-stable fodder)
	3) switch sock_alloc_file() to new calling conventions.

	It got some local testing, but it certainly needs more review.
Diffstat for the entire thing is
 drivers/staging/lustre/lnet/lnet/lib-socket.c |   8 ++---
 net/9p/trans_fd.c                             |   1 -
 net/kcm/kcmsock.c                             |  68 ++++++++++++++---------------------------
 net/sctp/socket.c                             |   1 -
 net/socket.c                                  | 110 +++++++++++++++++++++++++++----------------------------------------
 5 files changed, 69 insertions(+), 119 deletions(-)

	Please, review and comment.

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-12-05 23:41 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2017-12-05 23:29 [PATCH 3/3] make sock_alloc_file() do sock_release() on failures Al Viro
2017-12-05 23:41 ` David Miller
  -- strict thread matches above, loose matches on Subject: below --
2017-12-01  0:20 [RFC][PATCHES] sock_alloc_file() cleanups and fixes Al Viro
2017-12-01  0:23 ` [PATCH 3/3] make sock_alloc_file() do sock_release() on failures Al Viro
2017-12-01  9:33   ` Eric Dumazet

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