From dfd3d5266dc1d9a2b06e5a09bbff4cee547eeb5f Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 24 Jul 2020 08:48:55 +0200 Subject: sctp: fix slab-out-of-bounds in SCTP_DELAYED_SACK processing This sockopt accepts two kinds of parameters, using struct sctp_sack_info and struct sctp_assoc_value. The mentioned commit didn't notice an implicit cast from the smaller (latter) struct to the bigger one (former) when copying the data from the user space, which now leads to an attempt to write beyond the buffer (because it assumes the storing buffer is bigger than the parameter itself). Fix it by allocating a sctp_sack_info on stack and filling it out based on the small struct for the compat case. Changelog stole from an earlier patch from Marcelo Ricardo Leitner. Fixes: ebb25defdc17 ("sctp: pass a kernel pointer to sctp_setsockopt_delayed_ack") Reported-by: syzbot+0e4699d000d8b874d8dc@syzkaller.appspotmail.com Signed-off-by: Christoph Hellwig Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller --- net/sctp/socket.c | 50 +++++++++++++++++++++++++++++--------------------- 1 file changed, 29 insertions(+), 21 deletions(-) (limited to 'net/sctp') diff --git a/net/sctp/socket.c b/net/sctp/socket.c index 144808dfea9e..ec1fba1fbe71 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -2749,31 +2749,12 @@ static void sctp_apply_asoc_delayed_ack(struct sctp_sack_info *params, * timer to expire. The default value for this is 2, setting this * value to 1 will disable the delayed sack algorithm. */ - -static int sctp_setsockopt_delayed_ack(struct sock *sk, - struct sctp_sack_info *params, - unsigned int optlen) +static int __sctp_setsockopt_delayed_ack(struct sock *sk, + struct sctp_sack_info *params) { struct sctp_sock *sp = sctp_sk(sk); struct sctp_association *asoc; - if (optlen == sizeof(struct sctp_sack_info)) { - if (params->sack_delay == 0 && params->sack_freq == 0) - return 0; - } else if (optlen == sizeof(struct sctp_assoc_value)) { - pr_warn_ratelimited(DEPRECATED - "%s (pid %d) " - "Use of struct sctp_assoc_value in delayed_ack socket option.\n" - "Use struct sctp_sack_info instead\n", - current->comm, task_pid_nr(current)); - - if (params->sack_delay == 0) - params->sack_freq = 1; - else - params->sack_freq = 0; - } else - return -EINVAL; - /* Validate value parameter. */ if (params->sack_delay > 500) return -EINVAL; @@ -2821,6 +2802,33 @@ static int sctp_setsockopt_delayed_ack(struct sock *sk, return 0; } +static int sctp_setsockopt_delayed_ack(struct sock *sk, + struct sctp_sack_info *params, + unsigned int optlen) +{ + if (optlen == sizeof(struct sctp_assoc_value)) { + struct sctp_assoc_value *v = (struct sctp_assoc_value *)params; + struct sctp_sack_info p; + + pr_warn_ratelimited(DEPRECATED + "%s (pid %d) " + "Use of struct sctp_assoc_value in delayed_ack socket option.\n" + "Use struct sctp_sack_info instead\n", + current->comm, task_pid_nr(current)); + + p.sack_assoc_id = v->assoc_id; + p.sack_delay = v->assoc_value; + p.sack_freq = v->assoc_value ? 0 : 1; + return __sctp_setsockopt_delayed_ack(sk, &p); + } + + if (optlen != sizeof(struct sctp_sack_info)) + return -EINVAL; + if (params->sack_delay == 0 && params->sack_freq == 0) + return 0; + return __sctp_setsockopt_delayed_ack(sk, params); +} + /* 7.1.3 Initialization Parameters (SCTP_INITMSG) * * Applications can specify protocol parameters for the default association -- cgit v1.2.3