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Groups > linux.kernel > #1525922

[PATCH 4.4 11/37] sctp: assign assoc_id earlier in __sctp_connect

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>


[ Upstream commit 7233bc84a3aeda835d334499dc00448373caf5c0 ]

sctp_wait_for_connect() currently already holds the asoc to keep it
alive during the sleep, in case another thread release it. But Andrey
Konovalov and Dmitry Vyukov reported an use-after-free in such
situation.

Problem is that __sctp_connect() doesn't get a ref on the asoc and will
do a read on the asoc after calling sctp_wait_for_connect(), but by then
another thread may have closed it and the _put on sctp_wait_for_connect
will actually release it, causing the use-after-free.

Fix is, instead of doing the read after waiting for the connect, do it
before so, and avoid this issue as the socket is still locked by then.
There should be no issue on returning the asoc id in case of failure as
the application shouldn't trust on that number in such situations
anyway.

This issue doesn't exist in sctp_sendmsg() path.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sctp/socket.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1212,9 +1212,12 @@ static int __sctp_connect(struct sock *s
 
 	timeo = sock_sndtimeo(sk, f_flags & O_NONBLOCK);
 
-	err = sctp_wait_for_connect(asoc, &timeo);
-	if ((err == 0 || err == -EINPROGRESS) && assoc_id)
+	if (assoc_id)
 		*assoc_id = asoc->assoc_id;
+	err = sctp_wait_for_connect(asoc, &timeo);
+	/* Note: the asoc may be freed after the return of
+	 * sctp_wait_for_connect.
+	 */
 
 	/* Don't free association on exit. */
 	asoc = NULL;

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[PATCH 4.4 00/37] 4.4.34-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 31/37] sparc64: Convert U1copy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 02/37] net: clear sk_err_soft in sk_clone_lock() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 12/37] fib_trie: Correct /proc/net/route off by one error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 27/37] sparc64: Delete __ret_efault. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 25/37] sparc64: Fix illegal relative branches in hypervisor patched TLB cross-call code. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 10/37] ipv6: dccp: add missing bind_conflict to dccp_ipv6_mapped Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 32/37] sparc64: Convert NG4copy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 24/37] sparc64: Fix instruction count in comment for __hypervisor_flush_tlb_pending. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 07/37] dccp: do not send reset to already closed sockets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 14/37] net: __skb_flow_dissect() must cap its return value Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 30/37] sparc64: Convert GENcopy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 05/37] ip6_tunnel: Clear IP6CB in ip6tunnel_xmit() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 35/37] sparc64: Convert U3copy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 33/37] sparc64: Convert NGcopy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 11/37] sctp: assign assoc_id earlier in __sctp_connect Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 19/37] sparc: serial: sunhv: fix a double lock bug Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 16/37] tcp: take care of truncations done by sk_filter() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 23/37] sparc64: Fix illegal relative branches in hypervisor patched TLB code. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 36/37] sparc64: Delete now unused user copy assembler helpers. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 09/37] ipv6: dccp: fix out of bound access in dccp_v6_err() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 17/37] tty: Prevent ldisc drivers from re-using stale tty fields Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 26/37] sparc64: Handle extremely large kernel TLB range flushes more gracefully. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 29/37] sparc64: Convert copy_in_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 34/37] sparc64: Convert NG2copy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 15/37] ipv4: use new_gw for redirect neigh lookup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 37/37] sparc64: Delete now unused user copy fixup functions. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 01/37] dctcp: avoid bogus doubling of cwnd after loss Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 20/37] sparc64 mm: Fix base TSB sizing when hugetlb pages are used Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 04/37] bgmac: stop clearing DMA receive control register right after it is set Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 21/37] sparc: Handle negative offsets in arch_jump_label_transform Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 08/37] dccp: fix out of bound access in dccp_v4_err() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 22/37] sparc64: Handle extremely large kernel TSB range flushes sanely. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  Re: [PATCH 4.4 00/37] 4.4.34-stable review Guenter Roeck <linux@roeck-us.net> - 2016-11-19 17:30 +0100
  Re: [PATCH 4.4 00/37] 4.4.34-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-11-21 17:40 +0100
    Re: [PATCH 4.4 00/37] 4.4.34-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-21 17:50 +0100

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