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Message-ID: <20190201145840.GD10521@localhost.localdomain> Date: Fri, 1 Feb 2019 12:58:40 -0200 From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Cc: Vlad Yasevich <vyasevich@...il.com>, Neil Horman <nhorman@...driver.com>, linux-sctp@...r.kernel.org, netdev@...r.kernel.org, vuln@...unia.com Subject: Re: [PATCH net] sctp: walk the list of asoc safely On Fri, Feb 01, 2019 at 03:43:59PM +0100, Greg Kroah-Hartman wrote: > On Fri, Feb 01, 2019 at 12:20:37PM -0200, Marcelo Ricardo Leitner wrote: > > On Fri, Feb 01, 2019 at 03:15:22PM +0100, Greg Kroah-Hartman wrote: > > > In sctp_sendmesg(), when walking the list of endpoint associations, the > > > association can be dropped from the list, making the list corrupt. > > > Properly handle this by using list_for_each_entry_safe() > > > > > > Fixes: 4910280503f3 ("sctp: add support for snd flag SCTP_SENDALL process in sendmsg") > > > Reported-by: Secunia Research <vuln@...unia.com> > > > Tested-by: Secunia Research <vuln@...unia.com> > > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> > > > > > > diff --git a/net/sctp/socket.c b/net/sctp/socket.c > > > index f93c3cf9e567..65d6d04546ae 100644 > > > --- a/net/sctp/socket.c > > > +++ b/net/sctp/socket.c > > > @@ -2027,7 +2027,7 @@ static int sctp_sendmsg(struct sock *sk, struct msghdr *msg, size_t msg_len) > > > struct sctp_endpoint *ep = sctp_sk(sk)->ep; > > > struct sctp_transport *transport = NULL; > > > struct sctp_sndrcvinfo _sinfo, *sinfo; > > > - struct sctp_association *asoc; > > > + struct sctp_association *asoc, *tmp; > > > struct sctp_cmsgs cmsgs; > > > union sctp_addr *daddr; > > > bool new = false; > > > @@ -2053,7 +2053,7 @@ static int sctp_sendmsg(struct sock *sk, struct msghdr *msg, size_t msg_len) > > > > Extending the context here by 1 line: > > lock_sock(sk); > > > > > > /* SCTP_SENDALL process */ > > > if ((sflags & SCTP_SENDALL) && sctp_style(sk, UDP)) { > > > - list_for_each_entry(asoc, &ep->asocs, asocs) { > > > + list_for_each_entry_safe(asoc, tmp, &ep->asocs, asocs) { > > > > With the socket being locked by here, how can an asoc be removed > > while the list is being traversed? The socket lock should be > > protecting from it. > > What about when the SCTP_ABORT flag is set with SCTP_SENDALL at the same > time? > > :( Good point! Thanks. Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
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