[syzbot] [sctp?] general protection fault in sctp_outq_tail

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cdd28833100c net: microchip: sparx5: fix deletion of exist..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=1588fe92c80000
kernel config: https://syzkaller.appspot.com/x/.config?x=cab35c936731a347
dashboard link: https://syzkaller.appspot.com/bug?extid=47c24ca20a2fa01f082e
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d80ff4c80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f6e90ac80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2fb6257d1131/disk-cdd28833.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a3025d79117c/vmlinux-cdd28833.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8e6d670a5fed/bzImage-cdd28833.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+47c24c...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
CPU: 1 PID: 5783 Comm: syz-executor825 Not tainted 6.2.0-syzkaller-12889-gcdd28833100c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
RIP: 0010:list_add_tail include/linux/list.h:102 [inline]
RIP: 0010:sctp_outq_tail_data net/sctp/outqueue.c:91 [inline]
RIP: 0010:sctp_outq_tail+0x4ab/0xbf0 net/sctp/outqueue.c:299
Code: 8b 48 08 4c 8d 6b 18 48 8d 41 30 48 89 44 24 08 48 8d 41 38 48 89 c2 48 89 44 24 20 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 0a 06 00 00 4c 8b 79 38 4c 89 ef 48 89 4c 24 28
RSP: 0018:ffffc90005257568 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff888072779140 RCX: 0000000000000000
RDX: 0000000000000007 RSI: ffffffff841d7ef0 RDI: ffff888071fbb0c8
RBP: ffff8880787a47e0 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff92000a4aeb3
R13: ffff888072779158 R14: ffff8880787c0000 R15: ffff888071ad7c80
FS: 00007f5801104700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f58011b0740 CR3: 000000002a37e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
sctp_cmd_send_msg net/sctp/sm_sideeffect.c:1114 [inline]
sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1777 [inline]
sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline]
sctp_do_sm+0x197d/0x5310 net/sctp/sm_sideeffect.c:1170
sctp_primitive_SEND+0x9f/0xc0 net/sctp/primitive.c:163
sctp_sendmsg_to_asoc+0x10eb/0x1a30 net/sctp/socket.c:1868
sctp_sendmsg+0x8d4/0x1d90 net/sctp/socket.c:2026
inet_sendmsg+0x9d/0xe0 net/ipv4/af_inet.c:825
sock_sendmsg_nosec net/socket.c:722 [inline]
sock_sendmsg+0xde/0x190 net/socket.c:745
__sys_sendto+0x23a/0x340 net/socket.c:2145
__do_sys_sendto net/socket.c:2157 [inline]
__se_sys_sendto net/socket.c:2153 [inline]
__x64_sys_sendto+0xe1/0x1b0 net/socket.c:2153
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f5801177ce9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 15 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f58011042f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f58012004b8 RCX: 00007f5801177ce9
RDX: 0000000000034000 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00007f58012004b0 R08: 00000000200005c0 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f58012004bc
R13: 00007f58011cd600 R14: 0100000000000000 R15: 0000000000022000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:list_add_tail include/linux/list.h:102 [inline]
RIP: 0010:sctp_outq_tail_data net/sctp/outqueue.c:91 [inline]
RIP: 0010:sctp_outq_tail+0x4ab/0xbf0 net/sctp/outqueue.c:299
Code: 8b 48 08 4c 8d 6b 18 48 8d 41 30 48 89 44 24 08 48 8d 41 38 48 89 c2 48 89 44 24 20 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 0a 06 00 00 4c 8b 79 38 4c 89 ef 48 89 4c 24 28
RSP: 0018:ffffc90005257568 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff888072779140 RCX: 0000000000000000
RDX: 0000000000000007 RSI: ffffffff841d7ef0 RDI: ffff888071fbb0c8
RBP: ffff8880787a47e0 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff92000a4aeb3
R13: ffff888072779158 R14: ffff8880787c0000 R15: ffff888071ad7c80
FS: 00007f5801104700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd458c9960 CR3: 000000002a37e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 8b 48 08 mov 0x8(%rax),%ecx
3: 4c 8d 6b 18 lea 0x18(%rbx),%r13
7: 48 8d 41 30 lea 0x30(%rcx),%rax
b: 48 89 44 24 08 mov %rax,0x8(%rsp)
10: 48 8d 41 38 lea 0x38(%rcx),%rax
14: 48 89 c2 mov %rax,%rdx
17: 48 89 44 24 20 mov %rax,0x20(%rsp)
1c: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
23: fc ff df
26: 48 c1 ea 03 shr $0x3,%rdx
* 2a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
2e: 0f 85 0a 06 00 00 jne 0x63e
34: 4c 8b 79 38 mov 0x38(%rcx),%r15
38: 4c 89 ef mov %r13,%rdi
3b: 48 89 4c 24 28 mov %rcx,0x28(%rsp)


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Hillf Danton]

On 22 Mar 2023 17:39:53 -0700

> HEAD commit: cdd28833100c net: microchip: sparx5: fix deletion of exist..
> git tree: net

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f6e90ac80000

Check if ext is init-ed.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git cdd28833100c

--- x/net/sctp/outqueue.c
+++ y/net/sctp/outqueue.c
@@ -88,6 +88,8 @@ static inline void sctp_outq_tail_data(s

stream = sctp_chunk_stream_no(ch);
oute = SCTP_SO(&q->asoc->stream, stream)->ext;
+ if (!oute)
+ return;
list_add_tail(&ch->stream_list, &oute->outq);
}

--

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
general protection fault in sctp_sched_fcfs_dequeue

general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
CPU: 0 PID: 6276 Comm: syz-executor.1 Not tainted 6.2.0-syzkaller-12889-gcdd28833100c-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023

RIP: 0010:sctp_sched_fcfs_dequeue+0xcd/0x140 net/sctp/stream_sched.c:68
Code: 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 80 00 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5c 24 08 48 8d 7b 30 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 59 4c 8b 63 30 49 83 ec 18 e8 d0 a2 1c f8 4c 89 e6
RSP: 0018:ffffc9000365f4c0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffffffff89685ef3 RDI: 0000000000000030
RBP: ffff8880298307e0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888026cde0c0
R13: ffff88802adfe800 R14: ffffc9000365f5c8 R15: ffff8880271258d8
FS: 00007f0035bea700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000020034000 CR3: 000000001f088000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Call Trace:
<TASK>
sctp_outq_dequeue_data net/sctp/outqueue.c:76 [inline]
sctp_outq_flush_data+0x8bf/0x26a0 net/sctp/outqueue.c:1086
sctp_outq_flush net/sctp/outqueue.c:1219 [inline]
sctp_outq_uncork+0x17c/0x200 net/sctp/outqueue.c:766
sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1816 [inline]
sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline]
sctp_do_sm+0x25a5/0x5310 net/sctp/sm_sideeffect.c:1170

sctp_primitive_SEND+0x9f/0xc0 net/sctp/primitive.c:163
sctp_sendmsg_to_asoc+0x10eb/0x1a30 net/sctp/socket.c:1868
sctp_sendmsg+0x8d4/0x1d90 net/sctp/socket.c:2026
inet_sendmsg+0x9d/0xe0 net/ipv4/af_inet.c:825
sock_sendmsg_nosec net/socket.c:722 [inline]
sock_sendmsg+0xde/0x190 net/socket.c:745
__sys_sendto+0x23a/0x340 net/socket.c:2145
__do_sys_sendto net/socket.c:2157 [inline]
__se_sys_sendto net/socket.c:2153 [inline]
__x64_sys_sendto+0xe1/0x1b0 net/socket.c:2153
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

RIP: 0033:0x7f0034e8c0f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0035bea168 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f0034fac050 RCX: 00007f0034e8c0f9

RDX: 0000000000034000 RSI: 0000000020000080 RDI: 0000000000000003

RBP: 00007f0034ee7ae9 R08: 00000000200005c0 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffcb991317f R14: 00007f0035bea300 R15: 0000000000022000

</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---

RIP: 0010:sctp_sched_fcfs_dequeue+0xcd/0x140 net/sctp/stream_sched.c:68
Code: 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 80 00 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5c 24 08 48 8d 7b 30 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 59 4c 8b 63 30 49 83 ec 18 e8 d0 a2 1c f8 4c 89 e6
RSP: 0018:ffffc9000365f4c0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffffffff89685ef3 RDI: 0000000000000030
RBP: ffff8880298307e0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888026cde0c0
R13: ffff88802adfe800 R14: ffffc9000365f5c8 R15: ffff8880271258d8
FS: 00007f0035bea700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00005604e5e9d950 CR3: 000000001f088000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):

0: 89 fa mov %edi,%edx
2: 48 c1 ea 03 shr $0x3,%rdx
6: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
a: 0f 85 80 00 00 00 jne 0x90
10: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
17: fc ff df
1a: 49 8b 5c 24 08 mov 0x8(%r12),%rbx
1f: 48 8d 7b 30 lea 0x30(%rbx),%rdi
23: 48 89 fa mov %rdi,%rdx

26: 48 c1 ea 03 shr $0x3,%rdx
* 2a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction

2e: 75 59 jne 0x89
30: 4c 8b 63 30 mov 0x30(%rbx),%r12
34: 49 83 ec 18 sub $0x18,%r12
38: e8 d0 a2 1c f8 callq 0xf81ca30d
3d: 4c 89 e6 mov %r12,%rsi


Tested on:

commit: cdd28833 net: microchip: sparx5: fix deletion of exist..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
console output: https://syzkaller.appspot.com/x/log.txt?x=13ec7aa1c80000

kernel config: https://syzkaller.appspot.com/x/.config?x=cab35c936731a347
dashboard link: https://syzkaller.appspot.com/bug?extid=47c24ca20a2fa01f082e
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=1391497ac80000

[Hillf Danton]

On 22 Mar 2023 17:39:53 -0700

> HEAD commit: cdd28833100c net: microchip: sparx5: fix deletion of exist..
> git tree: net

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f6e90ac80000

Check if ext is init-ed.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git cdd28833100c

--- x/net/sctp/outqueue.c
+++ y/net/sctp/outqueue.c
@@ -88,6 +88,8 @@ static inline void sctp_outq_tail_data(s

stream = sctp_chunk_stream_no(ch);
oute = SCTP_SO(&q->asoc->stream, stream)->ext;
+ if (!oute)
+ return;
list_add_tail(&ch->stream_list, &oute->outq);
}

--- x/net/sctp/stream_sched.c
+++ y/net/sctp/stream_sched.c
@@ -65,6 +65,8 @@ static struct sctp_chunk *sctp_sched_fcf
goto out;

if (stream->out_curr) {
+ if (!stream->out_curr->ext)
+ return NULL;
ch = list_entry(stream->out_curr->ext->outq.next,
struct sctp_chunk, stream_list);
} else {
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+47c24c...@syzkaller.appspotmail.com

Tested on:

commit: cdd28833 net: microchip: sparx5: fix deletion of exist..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git

console output: https://syzkaller.appspot.com/x/log.txt?x=13650781c80000

kernel config: https://syzkaller.appspot.com/x/.config?x=cab35c936731a347
dashboard link: https://syzkaller.appspot.com/bug?extid=47c24ca20a2fa01f082e
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=1144c67ec80000

Note: testing is done by a robot and is best-effort only.

[Xin Long]

On Wed, Mar 22, 2023 at 8:39 PM syzbot
<syzbot+47c24c...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: cdd28833100c net: microchip: sparx5: fix deletion of exist..
> git tree: net
> console output: https://syzkaller.appspot.com/x/log.txt?x=1588fe92c80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=cab35c936731a347
> dashboard link: https://syzkaller.appspot.com/bug?extid=47c24ca20a2fa01f082e
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d80ff4c80000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f6e90ac80000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/2fb6257d1131/disk-cdd28833.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/a3025d79117c/vmlinux-cdd28833.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/8e6d670a5fed/bzImage-cdd28833.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+47c24c...@syzkaller.appspotmail.com
>
> general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
> CPU: 1 PID: 5783 Comm: syz-executor825 Not tainted 6.2.0-syzkaller-12889-gcdd28833100c #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
> RIP: 0010:list_add_tail include/linux/list.h:102 [inline]
> RIP: 0010:sctp_outq_tail_data net/sctp/outqueue.c:91 [inline]

The null-ptr-deref is 'SCTP_SO(&q->asoc->stream, stream)->ext' in
sctp_outq_tail_data(). It should be set in sctp_sendmsg_to_asoc(),
unless the out stream got shrunk by:

sctp_stream_update() -> sctp_stream_outq_migrate() ->
sctp_stream_shrink_out().

When sending msgs on a closed association, it will first do handshakes.
During the handshake, send more data with a big stream_num N until the
tx buffer is full and the sending is waiting for more buffer, then
after the handshakes are over and the big stream N is freed during the
handshakes(which may happen when peer doesn't support so many streams),
and the sending waiting for the tx buffer will try to enqueue data on a
freed out stream, then this issue occurred.

I will confirm this and give a fix.

Thanks.