[syzbot] [bpf?] general protection fault in bpf_check (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ddb2ffdc474a libbpf: Define MFD_CLOEXEC if not available
git tree: bpf
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14ba06a5180000
kernel config: https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=ba82760c63ba37799f70
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=115671f1180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14f14e31180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1e40c56954a9/disk-ddb2ffdc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/738240a7f62b/vmlinux-ddb2ffdc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2b2e360f1d3a/bzImage-ddb2ffdc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ba8276...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
CPU: 1 PID: 5066 Comm: syz-executor115 Not tainted 6.8.0-syzkaller-05232-gddb2ffdc474a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
RIP: 0010:do_misc_fixups kernel/bpf/verifier.c:19609 [inline]
RIP: 0010:bpf_check+0xa19b/0x19010 kernel/bpf/verifier.c:21294
Code: 48 c1 e8 03 80 3c 08 00 74 12 48 89 df e8 2d 93 50 00 48 b9 00 00 00 00 00 fc ff df 48 8b 1b 48 83 c3 30 48 89 d8 48 c1 e8 03 <0f> b6 04 08 84 c0 0f 85 e3 4c 00 00 8b 1b be 00 00 04 00 21 de 31
RSP: 0018:ffffc900039671e0 EFLAGS: 00010206
RAX: 0000000000000006 RBX: 0000000000000030 RCX: dffffc0000000000
RDX: ffff888018358000 RSI: 0000000000010000 RDI: 0000000000000001
RBP: ffffc90003967b50 R08: ffffffff81a7a128 R09: ffffffff81a7a365
R10: 0000000000000004 R11: ffff888018358000 R12: ffffc90000ace072
R13: 1ffff92000159c0e R14: 1ffff92000159c0e R15: 0000000000010000
FS: 000055555905c380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000111ed398 CR3: 000000002258e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
bpf_prog_load+0x1667/0x20f0 kernel/bpf/syscall.c:2895
__sys_bpf+0x4ee/0x810 kernel/bpf/syscall.c:5631
__do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f425974e3e9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe73dd9d38 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007ffe73dd9f18 RCX: 00007f425974e3e9
RDX: 0000000000000090 RSI: 00000000200000c0 RDI: 0000000000000005
RBP: 00007f42597c1610 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffe73dd9f08 R14: 0000000000000001 R15: 0000000000000001
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:do_misc_fixups kernel/bpf/verifier.c:19609 [inline]
RIP: 0010:bpf_check+0xa19b/0x19010 kernel/bpf/verifier.c:21294
Code: 48 c1 e8 03 80 3c 08 00 74 12 48 89 df e8 2d 93 50 00 48 b9 00 00 00 00 00 fc ff df 48 8b 1b 48 83 c3 30 48 89 d8 48 c1 e8 03 <0f> b6 04 08 84 c0 0f 85 e3 4c 00 00 8b 1b be 00 00 04 00 21 de 31
RSP: 0018:ffffc900039671e0 EFLAGS: 00010206
RAX: 0000000000000006 RBX: 0000000000000030 RCX: dffffc0000000000
RDX: ffff888018358000 RSI: 0000000000010000 RDI: 0000000000000001
RBP: ffffc90003967b50 R08: ffffffff81a7a128 R09: ffffffff81a7a365
R10: 0000000000000004 R11: ffff888018358000 R12: ffffc90000ace072
R13: 1ffff92000159c0e R14: 1ffff92000159c0e R15: 0000000000010000
FS: 000055555905c380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000111ed398 CR3: 000000002258e000 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 08 00 cmpb $0x0,(%rax,%rcx,1)
8: 74 12 je 0x1c
a: 48 89 df mov %rbx,%rdi
d: e8 2d 93 50 00 call 0x50933f
12: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx
19: fc ff df
1c: 48 8b 1b mov (%rbx),%rbx
1f: 48 83 c3 30 add $0x30,%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 0f b6 04 08 movzbl (%rax,%rcx,1),%eax <-- trapping instruction
2e: 84 c0 test %al,%al
30: 0f 85 e3 4c 00 00 jne 0x4d19
36: 8b 1b mov (%rbx),%ebx
38: be 00 00 04 00 mov $0x40000,%esi
3d: 21 de and %ebx,%esi
3f: 31 .byte 0x31


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[Jiri Olsa]

looks like we might have a fix already:
https://lore.kernel.org/bpf/20240322153518.1...@gmail.com/T/#u

jirka

[syzbot]

syzbot has bisected this issue to:

commit 6082b6c328b5486da2b356eae94b8b83c98b5565
Author: Alexei Starovoitov <a...@kernel.org>
Date: Fri Mar 8 01:08:03 2024 +0000

bpf: Recognize addr_space_cast instruction in the verifier.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=101f5ac9180000
start commit: ddb2ffdc474a libbpf: Define MFD_CLOEXEC if not available
git tree: bpf
final oops: https://syzkaller.appspot.com/x/report.txt?x=121f5ac9180000
console output: https://syzkaller.appspot.com/x/log.txt?x=141f5ac9180000

kernel config: https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=ba82760c63ba37799f70

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=115671f1180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14f14e31180000

Reported-by: syzbot+ba8276...@syzkaller.appspotmail.com
Fixes: 6082b6c328b5 ("bpf: Recognize addr_space_cast instruction in the verifier.")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection