Re: [PATCH 6.6.y] sctp: add mutual exclusion in proc_sctp_do_udp_port()

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 10206302af856791fbcc27a33ed3c3eb09b2793d

WARNING: Author mismatch between patch and upstream commit:
Backport author: <jianqi.ren.cn@windriver.com>
Commit author: Eric Dumazet<edumazet@google.com>

Status in newer kernel trees:
6.14.y | Present (different SHA1: d3d7675d7762)
6.12.y | Present (different SHA1: e5178bfc55b3)

Note: The patch differs from the upstream commit:
---
1:  10206302af856 ! 1:  413154924c580 sctp: add mutual exclusion in proc_sctp_do_udp_port()
    @@ Metadata
      ## Commit message ##
         sctp: add mutual exclusion in proc_sctp_do_udp_port()
     
    +    [ Upstream commit 10206302af856791fbcc27a33ed3c3eb09b2793d ]
    +
         We must serialize calls to sctp_udp_sock_stop() and sctp_udp_sock_start()
         or risk a crash as syzbot reported:
     
    @@ Commit message
         Acked-by: Xin Long <lucien.xin@gmail.com>
         Link: https://patch.msgid.link/20250331091532.224982-1-edumazet@google.com
         Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    +    [Minor conflict resolved due to code context change.]
    +    Signed-off-by: Jianqi Ren <jianqi.ren.cn@windriver.com>
    +    Signed-off-by: He Zhe <zhe.he@windriver.com>
     
      ## net/sctp/sysctl.c ##
    -@@ net/sctp/sysctl.c: static int proc_sctp_do_auth(const struct ctl_table *ctl, int write,
    +@@ net/sctp/sysctl.c: static int proc_sctp_do_auth(struct ctl_table *ctl, int write,
      	return ret;
      }
      
     +static DEFINE_MUTEX(sctp_sysctl_mutex);
     +
    - static int proc_sctp_do_udp_port(const struct ctl_table *ctl, int write,
    + static int proc_sctp_do_udp_port(struct ctl_table *ctl, int write,
      				 void *buffer, size_t *lenp, loff_t *ppos)
      {
    -@@ net/sctp/sysctl.c: static int proc_sctp_do_udp_port(const struct ctl_table *ctl, int write,
    +@@ net/sctp/sysctl.c: static int proc_sctp_do_udp_port(struct ctl_table *ctl, int write,
      		if (new_value > max || new_value < min)
      			return -EINVAL;
      
    @@ net/sctp/sysctl.c: static int proc_sctp_do_udp_port(const struct ctl_table *ctl,
      		net->sctp.udp_port = new_value;
      		sctp_udp_sock_stop(net);
      		if (new_value) {
    -@@ net/sctp/sysctl.c: static int proc_sctp_do_udp_port(const struct ctl_table *ctl, int write,
    +@@ net/sctp/sysctl.c: static int proc_sctp_do_udp_port(struct ctl_table *ctl, int write,
      		lock_sock(sk);
      		sctp_sk(sk)->udp_port = htons(net->sctp.udp_port);
      		release_sock(sk);
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.6.y        |  Success    |  Success   |