Subject: Re: [syzbot] [bpf?] [net?] general protection fault in dev_map_redirect

From: syzbot <[email-masked]>
Date: Fri, 05 Jul 2024 23:21:24 -0700

syzbot has found a reproducer for the following issue on:

HEAD commit:    0b58e108042b Add linux-next specific files for 20240703
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1228a3b9980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ed034204f2e40e53
dashboard link: https://syzkaller.appspot.com/bug?extid=08811615f0e17bc6708b
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12512bc1980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10fe346e980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1d079762feae/disk-0b58e108.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e53996c8d8c2/vmlinux-0b58e108.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a0bf21cdd844/bzImage-0b58e108.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
CPU: 1 UID: 0 PID: 5101 Comm: syz-executor153 Not tainted 6.10.0-rc6-next-20240703-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
RIP: 0010:bpf_net_ctx_get_ri include/linux/filter.h:788 [inline]
RIP: 0010:__bpf_xdp_redirect_map include/linux/filter.h:1699 [inline]
RIP: 0010:dev_map_redirect+0x65/0x6a0 kernel/bpf/devmap.c:1015
Code: 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 83 b3 3d 00 4c 8b 2b 4d 8d 7d 38 4c 89 fb 48 c1 eb 03 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 03 84 c0 0f 85 6e 04 00 00 41 8b 2f 89 ee 83 e6 02 31 ff
RSP: 0018:ffffc9000355f6e8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000007 RCX: ffff888018b78000
RDX: 0000000000000000 RSI: 000000000355f738 RDI: ffff8880183a2800
RBP: dffffc0000000000 R08: 0000000000000007 R09: ffffffff81b5ee2f
R10: 0000000000000004 R11: ffff888018b78000 R12: 000000000355f738
R13: 0000000000000000 R14: 0000000000000008 R15: 0000000000000038
FS:  000055557cbd4380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002000f000 CR3: 0000000078ac6000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 bpf_prog_ec9efaa32d58ce69+0x56/0x5a
 __bpf_prog_run include/linux/filter.h:691 [inline]
 bpf_prog_run_xdp include/net/xdp.h:514 [inline]
 bpf_prog_run_generic_xdp+0x679/0x14c0 net/core/dev.c:4962
 netif_receive_generic_xdp net/core/dev.c:5075 [inline]
 do_xdp_generic+0x673/0xb90 net/core/dev.c:5134
 tun_get_user+0x2805/0x4560 drivers/net/tun.c:1924
 tun_chr_write_iter+0x113/0x1f0 drivers/net/tun.c:2048
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xa72/0xc90 fs/read_write.c:590
 ksys_write+0x1a0/0x2c0 fs/read_write.c:643
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa9a2adcf90
Code: 40 00 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 80 3d 31 e1 07 00 00 74 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83 ec 28 48 89
RSP: 002b:00007ffd3cd09788 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fa9a2adcf90
RDX: 000000000000fdef RSI: 0000000020000100 RDI: 00000000000000c8
RBP: 0000000000000000 R08: 00007ffd3cd098b8 R09: 00007ffd3cd098b8
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:bpf_net_ctx_get_ri include/linux/filter.h:788 [inline]
RIP: 0010:__bpf_xdp_redirect_map include/linux/filter.h:1699 [inline]
RIP: 0010:dev_map_redirect+0x65/0x6a0 kernel/bpf/devmap.c:1015
Code: 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 83 b3 3d 00 4c 8b 2b 4d 8d 7d 38 4c 89 fb 48 c1 eb 03 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 03 84 c0 0f 85 6e 04 00 00 41 8b 2f 89 ee 83 e6 02 31 ff
RSP: 0018:ffffc9000355f6e8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000007 RCX: ffff888018b78000
RDX: 0000000000000000 RSI: 000000000355f738 RDI: ffff8880183a2800
RBP: dffffc0000000000 R08: 0000000000000007 R09: ffffffff81b5ee2f
R10: 0000000000000004 R11: ffff888018b78000 R12: 000000000355f738
R13: 0000000000000000 R14: 0000000000000008 R15: 0000000000000038
FS:  000055557cbd4380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002000f000 CR3: 0000000078ac6000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	48 c1 e8 03          	shr    $0x3,%rax
   4:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1)
   8:	74 08                	je     0x12
   a:	48 89 df             	mov    %rbx,%rdi
   d:	e8 83 b3 3d 00       	call   0x3db395
  12:	4c 8b 2b             	mov    (%rbx),%r13
  15:	4d 8d 7d 38          	lea    0x38(%r13),%r15
  19:	4c 89 fb             	mov    %r15,%rbx
  1c:	48 c1 eb 03          	shr    $0x3,%rbx
  20:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  27:	fc ff df
* 2a:	0f b6 04 03          	movzbl (%rbx,%rax,1),%eax <-- trapping instruction
  2e:	84 c0                	test   %al,%al
  30:	0f 85 6e 04 00 00    	jne    0x4a4
  36:	41 8b 2f             	mov    (%r15),%ebp
  39:	89 ee                	mov    %ebp,%esi
  3b:	83 e6 02             	and    $0x2,%esi
  3e:	31 ff                	xor    %edi,%edi

---
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