linux-kernel - Re: [syzbot] [bpf?] UBSAN: array-index-out-of-bounds in check_stack_range

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Date: Wed, 20 Mar 2024 01:02:03 -0700
From: syzbot <syzbot+33f4297b5f927648741a@...kaller.appspotmail.com>
To: eadavis@...com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bpf?] UBSAN: array-index-out-of-bounds in check_stack_range_initialized

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
UBSAN: array-index-out-of-bounds in check_stack_range_initialized

mio: -8, mao: -8, as: -2147483647, check_stack_range_initialized
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in kernel/bpf/verifier.c:7193:12
index -1 is out of range for type 'u8[8]' (aka 'unsigned char[8]')
CPU: 0 PID: 5496 Comm: syz-executor.0 Not tainted 6.8.0-syzkaller-05230-g114b5b3b4bde-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
 ubsan_epilogue lib/ubsan.c:217 [inline]
 __ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:415
 check_stack_range_initialized+0x13d8/0x1630 kernel/bpf/verifier.c:7193
 check_helper_mem_access+0x2eb/0xfa0 kernel/bpf/verifier.c:7297
 check_helper_call+0x263c/0x7220 kernel/bpf/verifier.c:10255
 do_check+0x9e29/0x10530 kernel/bpf/verifier.c:17804
 do_check_common+0x14bd/0x1dd0 kernel/bpf/verifier.c:20503
 do_check_main kernel/bpf/verifier.c:20594 [inline]
 bpf_check+0x136ab/0x19010 kernel/bpf/verifier.c:21264
 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: 0033:0x7fb440a7dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb4417ef0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fb440babf80 RCX: 00007fb440a7dda9
RDX: 0000000000000090 RSI: 00000000200000c0 RDI: 0000000000000005
RBP: 00007fb440aca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007fb440babf80 R15: 00007ffc0626c2f8
 </TASK>
---[ end trace ]---


Tested on:

commit:         114b5b3b bpf, arm64: fix bug in BPF_LDX_MEMSX
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=14084006180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=33f4297b5f927648741a
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16c4aa31180000