Re: [moderation/CI] Re: sctp: socket: refactor sctp_skb_recv_datagram to use ERR_PTR

#syz upstream

On Mon, Jul 20, 2026 at 3:26 PM syzbot ci
<[email protected]> wrote:
>
> syzbot ci has tested the following series
>
> [v4] sctp: socket: refactor sctp_skb_recv_datagram to use ERR_PTR
> https://lore.kernel.org/all/[email protected]
> * [PATCH net v4] sctp: socket: refactor sctp_skb_recv_datagram to use ERR_PTR
>
> and found the following issue:
> general protection fault in sctp_recvmsg
>
> Full report is available here:
> https://ci.syzbot.org/series/f979ded9-9743-486d-b911-69a904c9f4ad
>
> ***
>
> general protection fault in sctp_recvmsg
>
> tree:      net
> URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git
> base:      e13caf1c26587434f0b768193100440939c0fb91
> arch:      amd64
> compiler:  Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
> config:    https://ci.syzbot.org/builds/e4b39daf-f862-498e-8aeb-c22b5a168551/config
> syz repro: https://ci.syzbot.org/findings/1893a3b4-56e4-49d0-9865-4ff919f027b3/syz_repro
>
> Oops: general protection fault, probably for non-canonical address 0xdffffc000000000e: 0000 [#1] SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
> CPU: 0 UID: 0 PID: 5830 Comm: syz.2.19 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> RIP: 0010:sctp_recvmsg+0x28d/0xd60 net/sctp/socket.c:2135
> Code: ff 72 0d e8 35 6a d6 f6 41 89 ee e9 da 06 00 00 4c 89 7c 24 08 48 8d 7d 70 48 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <0f> b6 04 08 84 c0 0f 85 2f 08 00 00 4c 63 7d 70 4d 39 fe 4d 0f 43
> RSP: 0018:ffffc90003a8f838 EFLAGS: 00010202
> RAX: 000000000000000e RBX: ffff888115ad1c80 RCX: dffffc0000000000
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000070
> RBP: 0000000000000000 R08: 1ffff92000751ef4 R09: 1ffff11022b5a460
> R10: dffffc0000000000 R11: fffffbfff206639f R12: ffff888115ad22f0
> R13: ffffc90003a8fd00 R14: 0000000000000000 R15: 0000000000000300
> FS:  00007facf6b766c0(0000) GS:ffff88818dc17000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00002000000055c0 CR3: 000000010a812000 CR4: 00000000000006f0
> Call Trace:
>  <TASK>
>  sock_recvmsg_nosec net/socket.c:1128 [inline]
>  sock_recvmsg+0x166/0x1e0 net/socket.c:1148
>  ____sys_recvmsg+0x1e6/0x4a0 net/socket.c:2904
>  ___sys_recvmsg+0x213/0x5a0 net/socket.c:2946
>  do_recvmmsg+0x31a/0x7f0 net/socket.c:3041
>  __sys_recvmmsg net/socket.c:3115 [inline]
>  __do_sys_recvmmsg net/socket.c:3138 [inline]
>  __se_sys_recvmmsg net/socket.c:3131 [inline]
>  __x64_sys_recvmmsg+0x198/0x250 net/socket.c:3131
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7facf5d9ce59
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007facf6b76028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
> RAX: ffffffffffffffda RBX: 00007facf6015fa0 RCX: 00007facf5d9ce59
> RDX: 000000000400023c RSI: 00002000000055c0 RDI: 0000000000000004
> RBP: 00007facf5e32e6f R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000300 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007facf6016038 R14: 00007facf6015fa0 R15: 00007ffcc05d60d8
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:sctp_recvmsg+0x28d/0xd60 net/sctp/socket.c:2135
> Code: ff 72 0d e8 35 6a d6 f6 41 89 ee e9 da 06 00 00 4c 89 7c 24 08 48 8d 7d 70 48 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <0f> b6 04 08 84 c0 0f 85 2f 08 00 00 4c 63 7d 70 4d 39 fe 4d 0f 43
> RSP: 0018:ffffc90003a8f838 EFLAGS: 00010202
> RAX: 000000000000000e RBX: ffff888115ad1c80 RCX: dffffc0000000000
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000070
> RBP: 0000000000000000 R08: 1ffff92000751ef4 R09: 1ffff11022b5a460
> R10: dffffc0000000000 R11: fffffbfff206639f R12: ffff888115ad22f0
> R13: ffffc90003a8fd00 R14: 0000000000000000 R15: 0000000000000300
> FS:  00007facf6b766c0(0000) GS:ffff88818dc17000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00002000000055c0 CR3: 000000010a812000 CR4: 00000000000006f0
> ----------------
> Code disassembly (best guess):
>    0:   ff 72 0d                push   0xd(%rdx)
>    3:   e8 35 6a d6 f6          call   0xf6d66a3d
>    8:   41 89 ee                mov    %ebp,%r14d
>    b:   e9 da 06 00 00          jmp    0x6ea
>   10:   4c 89 7c 24 08          mov    %r15,0x8(%rsp)
>   15:   48 8d 7d 70             lea    0x70(%rbp),%rdi
>   19:   48 89 f8                mov    %rdi,%rax
>   1c:   48 c1 e8 03             shr    $0x3,%rax
>   20:   48 b9 00 00 00 00 00    movabs $0xdffffc0000000000,%rcx
>   27:   fc ff df
> * 2a:   0f b6 04 08             movzbl (%rax,%rcx,1),%eax <-- trapping instruction
>   2e:   84 c0                   test   %al,%al
>   30:   0f 85 2f 08 00 00       jne    0x865
>   36:   4c 63 7d 70             movslq 0x70(%rbp),%r15
>   3a:   4d 39 fe                cmp    %r15,%r14
>   3d:   4d                      rex.WRB
>   3e:   0f                      .byte 0xf
>   3f:   43                      rex.XB
>
>
> ***
>
> If these findings have caused you to resend the series or submit a
> separate fix, please add the following tag to your commit message:
>   Tested-by: [email protected]
>
> ---
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>
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