Subject: [syzbot] [bpf?] [net?] KMSAN: uninit-value in bpf_prog_test_run_xdp

From: syzbot <[email-masked]>
Date: Sun, 10 Mar 2024 01:16:23 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    3aaa8ce7a335 Merge tag 'mm-hotfixes-stable-2024-03-07-16-1..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13e5861e180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f8d2f8f66e9a667a
dashboard link: https://syzkaller.appspot.com/bug?extid=6856926fbb5e9b794e5c
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=10ed8171180000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13b728ae180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2a093f1b5a72/disk-3aaa8ce7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/efa5cb929ca6/vmlinux-3aaa8ce7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2b0c044e721b/bzImage-3aaa8ce7.xz

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

=====================================================
BUG: KMSAN: uninit-value in bpf_prog_test_run_xdp+0x1758/0x1a30 net/bpf/test_run.c:1277
 bpf_prog_test_run_xdp+0x1758/0x1a30 net/bpf/test_run.c:1277
 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

Uninit was stored to memory at:
 bpf_test_run+0x515/0xaf0
 bpf_prog_test_run_xdp+0xea5/0x1a30 net/bpf/test_run.c:1267
 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

Uninit was stored to memory at:
 ___bpf_prog_run+0x76dd/0xdb80
 __bpf_prog_run512+0xb5/0xe0 kernel/bpf/core.c:2227
 bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run_xdp include/net/xdp.h:514 [inline]
 bpf_test_run+0x42d/0xaf0 net/bpf/test_run.c:421
 bpf_prog_test_run_xdp+0xea5/0x1a30 net/bpf/test_run.c:1267
 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

Uninit was stored to memory at:
 ___bpf_prog_run+0x8567/0xdb80
 __bpf_prog_run512+0xb5/0xe0 kernel/bpf/core.c:2227
 bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run_xdp include/net/xdp.h:514 [inline]
 bpf_test_run+0x42d/0xaf0 net/bpf/test_run.c:421
 bpf_prog_test_run_xdp+0xea5/0x1a30 net/bpf/test_run.c:1267
 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_run512+0x45/0xe0 kernel/bpf/core.c:2227
 bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
 __bpf_prog_run include/linux/filter.h:651 [inline]
 bpf_prog_run_xdp include/net/xdp.h:514 [inline]
 bpf_test_run+0x42d/0xaf0 net/bpf/test_run.c:421

CPU: 0 PID: 5009 Comm: syz-executor369 Not tainted 6.8.0-rc7-syzkaller-00142-g3aaa8ce7a335 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
=====================================================

---
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