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Date: Mon, 3 Jun 2019 14:14:52 -0400
From: Neil Horman <nhorman@...driver.com>
To: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc: linux-sctp@...r.kernel.org,
syzbot+f7e9153b037eac9b1df8@...kaller.appspotmail.com,
"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] Fix memory leak in sctp_process_init
On Mon, Jun 03, 2019 at 11:31:13AM -0300, Marcelo Ricardo Leitner wrote:
> On Mon, Jun 03, 2019 at 10:21:12AM -0400, Neil Horman wrote:
> > syzbot found the following leak in sctp_process_init
> > BUG: memory leak
> > unreferenced object 0xffff88810ef68400 (size 1024):
> > comm "syz-executor273", pid 7046, jiffies 4294945598 (age 28.770s)
> > hex dump (first 32 bytes):
> > 1d de 28 8d de 0b 1b e3 b5 c2 f9 68 fd 1a 97 25 ..(........h...%
> > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> > backtrace:
> > [<00000000a02cebbd>] kmemleak_alloc_recursive include/linux/kmemleak.h:55
> > [inline]
> > [<00000000a02cebbd>] slab_post_alloc_hook mm/slab.h:439 [inline]
> > [<00000000a02cebbd>] slab_alloc mm/slab.c:3326 [inline]
> > [<00000000a02cebbd>] __do_kmalloc mm/slab.c:3658 [inline]
> > [<00000000a02cebbd>] __kmalloc_track_caller+0x15d/0x2c0 mm/slab.c:3675
> > [<000000009e6245e6>] kmemdup+0x27/0x60 mm/util.c:119
> > [<00000000dfdc5d2d>] kmemdup include/linux/string.h:432 [inline]
> > [<00000000dfdc5d2d>] sctp_process_init+0xa7e/0xc20
> > net/sctp/sm_make_chunk.c:2437
> > [<00000000b58b62f8>] sctp_cmd_process_init net/sctp/sm_sideeffect.c:682
> > [inline]
> > [<00000000b58b62f8>] sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1384
> > [inline]
> > [<00000000b58b62f8>] sctp_side_effects net/sctp/sm_sideeffect.c:1194
> > [inline]
> > [<00000000b58b62f8>] sctp_do_sm+0xbdc/0x1d60 net/sctp/sm_sideeffect.c:1165
> > [<0000000044e11f96>] sctp_assoc_bh_rcv+0x13c/0x200
> > net/sctp/associola.c:1074
> > [<00000000ec43804d>] sctp_inq_push+0x7f/0xb0 net/sctp/inqueue.c:95
> > [<00000000726aa954>] sctp_backlog_rcv+0x5e/0x2a0 net/sctp/input.c:354
> > [<00000000d9e249a8>] sk_backlog_rcv include/net/sock.h:950 [inline]
> > [<00000000d9e249a8>] __release_sock+0xab/0x110 net/core/sock.c:2418
> > [<00000000acae44fa>] release_sock+0x37/0xd0 net/core/sock.c:2934
> > [<00000000963cc9ae>] sctp_sendmsg+0x2c0/0x990 net/sctp/socket.c:2122
> > [<00000000a7fc7565>] inet_sendmsg+0x64/0x120 net/ipv4/af_inet.c:802
> > [<00000000b732cbd3>] sock_sendmsg_nosec net/socket.c:652 [inline]
> > [<00000000b732cbd3>] sock_sendmsg+0x54/0x70 net/socket.c:671
> > [<00000000274c57ab>] ___sys_sendmsg+0x393/0x3c0 net/socket.c:2292
> > [<000000008252aedb>] __sys_sendmsg+0x80/0xf0 net/socket.c:2330
> > [<00000000f7bf23d1>] __do_sys_sendmsg net/socket.c:2339 [inline]
> > [<00000000f7bf23d1>] __se_sys_sendmsg net/socket.c:2337 [inline]
> > [<00000000f7bf23d1>] __x64_sys_sendmsg+0x23/0x30 net/socket.c:2337
> > [<00000000a8b4131f>] do_syscall_64+0x76/0x1a0 arch/x86/entry/common.c:3
> >
> > The problem was that the peer.cookie value points to an skb allocated
> > area on the first pass through this function, at which point it is
> > overwritten with a heap allocated value, but in certain cases, where a
> > COOKIE_ECHO chunk is included in the packet, a second pass through
> > sctp_process_init is made, where the cookie value is re-allocated,
> > leaking the first allocation.
> >
> > Fix is to always allocate the cookie value, and free it when we are done
> > using it.
> >
> > Signed-off-by: Neil Horman <nhorman@...driver.com>
> > Reported-by: syzbot+f7e9153b037eac9b1df8@...kaller.appspotmail.com
> > CC: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> > CC: "David S. Miller" <davem@...emloft.net>
> > CC: netdev@...r.kernel.org
> > ---
> > net/sctp/associola.c | 1 +
> > net/sctp/sm_make_chunk.c | 12 +++---------
> > net/sctp/sm_sideeffect.c | 5 +++++
> > 3 files changed, 9 insertions(+), 9 deletions(-)
> >
> > diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> > index d2c7d0d2abc1..718b9917844e 100644
> > --- a/net/sctp/associola.c
> > +++ b/net/sctp/associola.c
> > @@ -393,6 +393,7 @@ void sctp_association_free(struct sctp_association *asoc)
> > kfree(asoc->peer.peer_random);
> > kfree(asoc->peer.peer_chunks);
> > kfree(asoc->peer.peer_hmacs);
> > + kfree(asoc->peer.cookie);
>
> This one slipped back..
>
Ah, thanks, I forgot to clean that up.
> >
> > /* Release the transport structures. */
> > list_for_each_safe(pos, temp, &asoc->peer.transport_addr_list) {
> > diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> > index 72e74503f9fc..ff365f22a3c1 100644
> > --- a/net/sctp/sm_make_chunk.c
> > +++ b/net/sctp/sm_make_chunk.c
> > @@ -2431,14 +2431,6 @@ int sctp_process_init(struct sctp_association *asoc, struct sctp_chunk *chunk,
> > /* Peer Rwnd : Current calculated value of the peer's rwnd. */
> > asoc->peer.rwnd = asoc->peer.i.a_rwnd;
> >
> > - /* Copy cookie in case we need to resend COOKIE-ECHO. */
> > - cookie = asoc->peer.cookie;
> > - if (cookie) {
> > - asoc->peer.cookie = kmemdup(cookie, asoc->peer.cookie_len, gfp);
> > - if (!asoc->peer.cookie)
> > - goto clean_up;
> > - }
>
> cookie will be left unused after this. May as well remove it too.
>
Yup, will do. V2 soon
> Marcelo
>
> > -
> > /* RFC 2960 7.2.1 The initial value of ssthresh MAY be arbitrarily
> > * high (for example, implementations MAY use the size of the receiver
> > * advertised window).
> > @@ -2607,7 +2599,9 @@ static int sctp_process_param(struct sctp_association *asoc,
> > case SCTP_PARAM_STATE_COOKIE:
> > asoc->peer.cookie_len =
> > ntohs(param.p->length) - sizeof(struct sctp_paramhdr);
> > - asoc->peer.cookie = param.cookie->body;
> > + asoc->peer.cookie = kmemdup(param.cookie->body, asoc->peer.cookie_len, gfp);
> > + if (!asoc->peer.cookie)
> > + retval = 0;
> > break;
> >
> > case SCTP_PARAM_HEARTBEAT_INFO:
> > diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
> > index 4aa03588f87b..27ddf2d8f001 100644
> > --- a/net/sctp/sm_sideeffect.c
> > +++ b/net/sctp/sm_sideeffect.c
> > @@ -898,6 +898,11 @@ static void sctp_cmd_new_state(struct sctp_cmd_seq *cmds,
> > asoc->rto_initial;
> > }
> >
> > + if (sctp_state(asoc, ESTABLISHED)) {
> > + kfree(asoc->peer.cookie);
> > + asoc->peer.cookie = NULL;
> > + }
> > +
> > if (sctp_state(asoc, ESTABLISHED) ||
> > sctp_state(asoc, CLOSED) ||
> > sctp_state(asoc, SHUTDOWN_RECEIVED)) {
> > --
> > 2.20.1
> >
>
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