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

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Date: Sun, 21 Jan 2024 23:46:19 -0800
From: syzbot <syzbot+853242d9c9917165d791@...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: Re: [syzbot] [bpf?] KMSAN: uninit-value in ___bpf_prog_run (4)

syzbot has found a reproducer for the following issue on:

HEAD commit:    9f8413c4a66f Merge tag 'cgroup-for-6.8' of git://git.kerne..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1493fa3de80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=656820e61b758b15
dashboard link: https://syzkaller.appspot.com/bug?extid=853242d9c9917165d791
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=139d21e7e80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12d6066fe80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/79d9f2f4b065/disk-9f8413c4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cbc68430d9c6/vmlinux-9f8413c4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9740ad9fc172/bzImage-9f8413c4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+853242d9c9917165d791@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in ___bpf_prog_run+0xa766/0xdb80 kernel/bpf/core.c:2037
 ___bpf_prog_run+0xa766/0xdb80 kernel/bpf/core.c:2037
 __bpf_prog_run512+0xb5/0xe0 kernel/bpf/core.c:2203
 bpf_dispatcher_nop_func include/linux/bpf.h:1196 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run include/linux/filter.h:658 [inline]
 bpf_test_run+0x482/0xb00 net/bpf/test_run.c:423
 bpf_prog_test_run_skb+0x14e5/0x1f20 net/bpf/test_run.c:1045
 bpf_prog_test_run+0x6af/0xac0 kernel/bpf/syscall.c:4040
 __sys_bpf+0x649/0xd60 kernel/bpf/syscall.c:5401
 __do_sys_bpf kernel/bpf/syscall.c:5487 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5485 [inline]
 __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5485
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was stored to memory at:
 ___bpf_prog_run+0x8567/0xdb80
 __bpf_prog_run512+0xb5/0xe0 kernel/bpf/core.c:2203
 bpf_dispatcher_nop_func include/linux/bpf.h:1196 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run include/linux/filter.h:658 [inline]
 bpf_test_run+0x482/0xb00 net/bpf/test_run.c:423
 bpf_prog_test_run_skb+0x14e5/0x1f20 net/bpf/test_run.c:1045
 bpf_prog_test_run+0x6af/0xac0 kernel/bpf/syscall.c:4040
 __sys_bpf+0x649/0xd60 kernel/bpf/syscall.c:5401
 __do_sys_bpf kernel/bpf/syscall.c:5487 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5485 [inline]
 __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5485
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Local variable stack created at:
 __bpf_prog_run512+0x45/0xe0 kernel/bpf/core.c:2203
 bpf_dispatcher_nop_func include/linux/bpf.h:1196 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run include/linux/filter.h:658 [inline]
 bpf_test_run+0x482/0xb00 net/bpf/test_run.c:423

CPU: 0 PID: 5010 Comm: syz-executor315 Not tainted 6.7.0-syzkaller-00562-g9f8413c4a66f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
=====================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.