[syzbot ci] Re: net: devmem: improve cpu cost of RX token management

[syzbot ci <syzbot+ci88b77c4aee0f7057@syzkaller.appspotmail.com>]

syzbot ci has tested the following series

[v4] net: devmem: improve cpu cost of RX token management
https://lore.kernel.org/all/20250926-scratch-bobbyeshleman-devmem-tcp-token-upstream-v4-0-39156563c3ea@meta.com
* [PATCH net-next v4 1/2] net: devmem: rename tx_vec to vec in dmabuf binding
* [PATCH net-next v4 2/2] net: devmem: use niov array for token management

and found the following issue:
general protection fault in sock_devmem_dontneed

Full report is available here:
https://ci.syzbot.org/series/b8209bd4-e9f0-4c54-bad3-613e8431151b

***

general protection fault in sock_devmem_dontneed

tree:      net-next
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git
base:      dc1dea796b197aba2c3cae25bfef45f4b3ad46fe
arch:      amd64
compiler:  Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
config:    https://ci.syzbot.org/builds/b4d90fd9-9fbe-4e17-8fc0-3d6603df09da/config
C repro:   https://ci.syzbot.org/findings/ce81b3c3-3db8-4643-9731-cbe331c65fdb/c_repro
syz repro: https://ci.syzbot.org/findings/ce81b3c3-3db8-4643-9731-cbe331c65fdb/syz_repro

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 UID: 0 PID: 5996 Comm: syz.0.17 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:sock_devmem_dontneed+0x372/0x920 net/core/sock.c:1113
Code: 48 44 8b 20 44 89 74 24 54 45 01 f4 48 8b 44 24 60 42 80 3c 28 00 74 08 48 89 df e8 e8 5a c9 f8 4c 8b 33 4c 89 f0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 cf 5a c9 f8 4d 8b 3e 4c 89 f8 48
RSP: 0018:ffffc90002a1fac0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88810a8ab710 RCX: 1ffff11023002f45
RDX: ffff88801b339cc0 RSI: 0000000000002000 RDI: 0000000000000000
RBP: ffffc90002a1fc50 R08: ffffc90002a1fbdf R09: 0000000000000000
R10: ffffc90002a1fb60 R11: fffff52000543f7c R12: 0000000000f07000
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff88810a8ab710
FS:  000055556f85a500(0000) GS:ffff8881a3c3d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000a2000 CR3: 0000000024516000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 sk_setsockopt+0x682/0x2dc0 net/core/sock.c:1304
 do_sock_setsockopt+0x11b/0x1b0 net/socket.c:2340
 __sys_setsockopt net/socket.c:2369 [inline]
 __do_sys_setsockopt net/socket.c:2375 [inline]
 __se_sys_setsockopt net/socket.c:2372 [inline]
 __x64_sys_setsockopt+0x13f/0x1b0 net/socket.c:2372
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fea0438ec29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd04a8f368 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007fea045d5fa0 RCX: 00007fea0438ec29
RDX: 0000000000000050 RSI: 0000000000000001 RDI: 0000000000000003
RBP: 00007fea04411e41 R08: 0000000000000010 R09: 0000000000000000
R10: 00002000000a2000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fea045d5fa0 R14: 00007fea045d5fa0 R15: 0000000000000005
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:sock_devmem_dontneed+0x372/0x920 net/core/sock.c:1113
Code: 48 44 8b 20 44 89 74 24 54 45 01 f4 48 8b 44 24 60 42 80 3c 28 00 74 08 48 89 df e8 e8 5a c9 f8 4c 8b 33 4c 89 f0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 cf 5a c9 f8 4d 8b 3e 4c 89 f8 48
RSP: 0018:ffffc90002a1fac0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88810a8ab710 RCX: 1ffff11023002f45
RDX: ffff88801b339cc0 RSI: 0000000000002000 RDI: 0000000000000000
RBP: ffffc90002a1fc50 R08: ffffc90002a1fbdf R09: 0000000000000000
R10: ffffc90002a1fb60 R11: fffff52000543f7c R12: 0000000000f07000
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff88810a8ab710
FS:  000055556f85a500(0000) GS:ffff8881a3c3d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000a2000 CR3: 0000000024516000 CR4: 00000000000006f0
----------------
Code disassembly (best guess):
   0:	48                   	rex.W
   1:	44 8b 20             	mov    (%rax),%r12d
   4:	44 89 74 24 54       	mov    %r14d,0x54(%rsp)
   9:	45 01 f4             	add    %r14d,%r12d
   c:	48 8b 44 24 60       	mov    0x60(%rsp),%rax
  11:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1)
  16:	74 08                	je     0x20
  18:	48 89 df             	mov    %rbx,%rdi
  1b:	e8 e8 5a c9 f8       	call   0xf8c95b08
  20:	4c 8b 33             	mov    (%rbx),%r14
  23:	4c 89 f0             	mov    %r14,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1) <-- trapping instruction
  2f:	74 08                	je     0x39
  31:	4c 89 f7             	mov    %r14,%rdi
  34:	e8 cf 5a c9 f8       	call   0xf8c95b08
  39:	4d 8b 3e             	mov    (%r14),%r15
  3c:	4c 89 f8             	mov    %r15,%rax
  3f:	48                   	rex.W


***

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: syzbot@syzkaller.appspotmail.com

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This report is generated by a bot. It may contain errors.
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