From a05d2ad1c1f391c7f514a1d1e09b5417968a7d07 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sun, 24 Apr 2011 01:54:57 +0000 Subject: af_unix: Only allow recv on connected seqpacket sockets. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This fixes the following oops discovered by Dan Aloni: > Anyway, the following is the output of the Oops that I got on the > Ubuntu kernel on which I first detected the problem > (2.6.37-12-generic). The Oops that followed will be more useful, I > guess. >[ 5594.669852] BUG: unable to handle kernel NULL pointer dereference > at           (null) > [ 5594.681606] IP: [] unix_dgram_recvmsg+0x1fb/0x420 > [ 5594.687576] PGD 2a05d067 PUD 2b951067 PMD 0 > [ 5594.693720] Oops: 0002 [#1] SMP > [ 5594.699888] last sysfs file: The bug was that unix domain sockets use a pseduo packet for connecting and accept uses that psudo packet to get the socket. In the buggy seqpacket case we were allowing unconnected sockets to call recvmsg and try to receive the pseudo packet. That is always wrong and as of commit 7361c36c5 the pseudo packet had become enough different from a normal packet that the kernel started oopsing. Do for seqpacket_recv what was done for seqpacket_send in 2.5 and only allow it on connected seqpacket sockets. Cc: stable@kernel.org Tested-by: Dan Aloni Signed-off-by: Eric W. Biederman Signed-off-by: David S. Miller --- net/unix/af_unix.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) (limited to 'net/unix/af_unix.c') diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 3a43a830476..b1d75beb7e2 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -524,6 +524,8 @@ static int unix_dgram_connect(struct socket *, struct sockaddr *, int, int); static int unix_seqpacket_sendmsg(struct kiocb *, struct socket *, struct msghdr *, size_t); +static int unix_seqpacket_recvmsg(struct kiocb *, struct socket *, + struct msghdr *, size_t, int); static const struct proto_ops unix_stream_ops = { .family = PF_UNIX, @@ -583,7 +585,7 @@ static const struct proto_ops unix_seqpacket_ops = { .setsockopt = sock_no_setsockopt, .getsockopt = sock_no_getsockopt, .sendmsg = unix_seqpacket_sendmsg, - .recvmsg = unix_dgram_recvmsg, + .recvmsg = unix_seqpacket_recvmsg, .mmap = sock_no_mmap, .sendpage = sock_no_sendpage, }; @@ -1699,6 +1701,18 @@ static int unix_seqpacket_sendmsg(struct kiocb *kiocb, struct socket *sock, return unix_dgram_sendmsg(kiocb, sock, msg, len); } +static int unix_seqpacket_recvmsg(struct kiocb *iocb, struct socket *sock, + struct msghdr *msg, size_t size, + int flags) +{ + struct sock *sk = sock->sk; + + if (sk->sk_state != TCP_ESTABLISHED) + return -ENOTCONN; + + return unix_dgram_recvmsg(iocb, sock, msg, size, flags); +} + static void unix_copy_addr(struct msghdr *msg, struct sock *sk) { struct unix_sock *u = unix_sk(sk); -- cgit v1.2.3-18-g5258 From 71338aa7d050c86d8765cd36e46be514fb0ebbce Mon Sep 17 00:00:00 2001 From: Dan Rosenberg Date: Mon, 23 May 2011 12:17:35 +0000 Subject: net: convert %p usage to %pK The %pK format specifier is designed to hide exposed kernel pointers, specifically via /proc interfaces. Exposing these pointers provides an easy target for kernel write vulnerabilities, since they reveal the locations of writable structures containing easily triggerable function pointers. The behavior of %pK depends on the kptr_restrict sysctl. If kptr_restrict is set to 0, no deviation from the standard %p behavior occurs. If kptr_restrict is set to 1, the default, if the current user (intended to be a reader via seq_printf(), etc.) does not have CAP_SYSLOG (currently in the LSM tree), kernel pointers using %pK are printed as 0's. If kptr_restrict is set to 2, kernel pointers using %pK are printed as 0's regardless of privileges. Replacing with 0's was chosen over the default "(null)", which cannot be parsed by userland %p, which expects "(nil)". The supporting code for kptr_restrict and %pK are currently in the -mm tree. This patch converts users of %p in net/ to %pK. Cases of printing pointers to the syslog are not covered, since this would eliminate useful information for postmortem debugging and the reading of the syslog is already optionally protected by the dmesg_restrict sysctl. Signed-off-by: Dan Rosenberg Cc: James Morris Cc: Eric Dumazet Cc: Thomas Graf Cc: Eugene Teo Cc: Kees Cook Cc: Ingo Molnar Cc: David S. Miller Cc: Peter Zijlstra Cc: Eric Paris Signed-off-by: Andrew Morton Signed-off-by: David S. Miller --- net/unix/af_unix.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/unix/af_unix.c') diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index b1d75beb7e2..0722a25a3a3 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2254,7 +2254,7 @@ static int unix_seq_show(struct seq_file *seq, void *v) struct unix_sock *u = unix_sk(s); unix_state_lock(s); - seq_printf(seq, "%p: %08X %08X %08X %04X %02X %5lu", + seq_printf(seq, "%pK: %08X %08X %08X %04X %02X %5lu", s, atomic_read(&s->sk_refcnt), 0, -- cgit v1.2.3-18-g5258