From 4aeda42a1b443d705980c85184cca7f8f28625bf Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Sat, 4 Sep 2010 01:34:28 +0000 Subject: [PATCH] UNIX: Do not loop forever at unix_autobind(). [ Upstream commit a9117426d0fcc05a194f728159a2d43df43c7add ] We assumed that unix_autobind() never fails if kzalloc() succeeded. But unix_autobind() allows only 1048576 names. If /proc/sys/fs/file-max is larger than 1048576 (e.g. systems with more than 10GB of RAM), a local user can consume all names using fork()/socket()/bind(). If all names are in use, those who call bind() with addr_len == sizeof(short) or connect()/sendmsg() with setsockopt(SO_PASSCRED) will continue while (1) yield(); loop at unix_autobind() till a name becomes available. This patch adds a loop counter in order to give up after 1048576 attempts. Calling yield() for once per 256 attempts may not be sufficient when many names are already in use, for __unix_find_socket_byname() can take long time under such circumstance. Therefore, this patch also adds cond_resched() call. Note that currently a local user can consume 2GB of kernel memory if the user is allowed to create and autobind 1048576 UNIX domain sockets. We should consider adding some restriction for autobind operation. Signed-off-by: Tetsuo Handa Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/unix/af_unix.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index fef2cc5e9d2b..617bea46486d 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -673,6 +673,7 @@ static int unix_autobind(struct socket *sock) static u32 ordernum = 1; struct unix_address *addr; int err; + unsigned int retries = 0; mutex_lock(&u->readlock); @@ -698,9 +699,17 @@ retry: if (__unix_find_socket_byname(net, addr->name, addr->len, sock->type, addr->hash)) { spin_unlock(&unix_table_lock); - /* Sanity yield. It is unusual case, but yet... */ - if (!(ordernum&0xFF)) - yield(); + /* + * __unix_find_socket_byname() may take long time if many names + * are already in use. + */ + cond_resched(); + /* Give up if all names seems to be in use. */ + if (retries++ == 0xFFFFF) { + err = -ENOSPC; + kfree(addr); + goto out; + } goto retry; } addr->hash ^= sk->sk_type; -- 2.11.0