linux-kernel - [syzbot] [bpf?] KMSAN: uninit-value in bpf_bprintf

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Date: Wed, 21 Feb 2024 12:55:22 -0800
From: syzbot <syzbot+c2dc95f7d0825a145992@...kaller.appspotmail.com>
To: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org, 
	daniel@...earbox.net, haoluo@...gle.com, john.fastabend@...il.com, 
	jolsa@...nel.org, kpsingh@...nel.org, linux-kernel@...r.kernel.org, 
	martin.lau@...ux.dev, sdf@...gle.com, song@...nel.org, 
	syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev
Subject: [syzbot] [bpf?] KMSAN: uninit-value in bpf_bprintf_prepare

Hello,

syzbot found the following issue on:

HEAD commit:    c1ca10ceffbb Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1364db0c180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e3dd779fba027968
dashboard link: https://syzkaller.appspot.com/bug?extid=c2dc95f7d0825a145992
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/83d019f0ac47/disk-c1ca10ce.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/49e05dd7a23d/vmlinux-c1ca10ce.xz
kernel image: https://storage.googleapis.com/syzbot-assets/68ec9fa2d33d/bzImage-c1ca10ce.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c2dc95f7d0825a145992@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in bpf_bprintf_prepare+0x20d7/0x23b0 kernel/bpf/helpers.c:904
 bpf_bprintf_prepare+0x20d7/0x23b0 kernel/bpf/helpers.c:904
 ____bpf_snprintf kernel/bpf/helpers.c:1060 [inline]
 bpf_snprintf+0x141/0x360 kernel/bpf/helpers.c:1044
 ___bpf_prog_run+0x2180/0xdb80 kernel/bpf/core.c:1986
 __bpf_prog_run288+0xb5/0xe0 kernel/bpf/core.c:2226
 bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run include/linux/filter.h:658 [inline]
 bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline]
 bpf_flow_dissect+0x127/0x470 net/core/flow_dissector.c:991
 bpf_prog_test_run_flow_dissector+0x6f4/0xa20 net/bpf/test_run.c:1359
 bpf_prog_test_run+0x6af/0xac0 kernel/bpf/syscall.c:4107
 __sys_bpf+0x649/0xd60 kernel/bpf/syscall.c:5475
 __do_sys_bpf kernel/bpf/syscall.c:5561 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5559 [inline]
 __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5559
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Local variable stack created at:
 __bpf_prog_run288+0x45/0xe0 kernel/bpf/core.c:2226
 bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run include/linux/filter.h:658 [inline]
 bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline]
 bpf_flow_dissect+0x127/0x470 net/core/flow_dissector.c:991

CPU: 0 PID: 6318 Comm: syz-executor.2 Not tainted 6.8.0-rc4-syzkaller-00331-gc1ca10ceffbb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
=====================================================


---
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