[syzbot] [bpf?] KMSAN: uninit-value in bstr_printf (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 614da38e2f7a Merge tag 'hid-for-linus-2024051401' of git:/..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=133d9a36980000
kernel config: https://syzkaller.appspot.com/x/.config?x=f5d2cbf33633f507
dashboard link: https://syzkaller.appspot.com/bug?extid=3d98610f9d9bdb4a57ce
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=1631e6f6980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=160d3126980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/89eafb874b71/disk-614da38e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/356000512ad9/vmlinux-614da38e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/839c73939115/bzImage-614da38e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3d9861...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in bstr_printf+0x19df/0x1b50 lib/vsprintf.c:3334
bstr_printf+0x19df/0x1b50 lib/vsprintf.c:3334
____bpf_snprintf kernel/bpf/helpers.c:1064 [inline]
bpf_snprintf+0x1c8/0x360 kernel/bpf/helpers.c:1044
___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
__bpf_prog_run288+0xb5/0xe0 kernel/bpf/core.c:2237
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
bpf_test_run+0x499/0xc30 net/bpf/test_run.c:425
bpf_prog_test_run_skb+0x14ea/0x1f20 net/bpf/test_run.c:1058
bpf_prog_test_run+0x6b7/0xad0 kernel/bpf/syscall.c:4269
__sys_bpf+0x6aa/0xd90 kernel/bpf/syscall.c:5678
__do_sys_bpf kernel/bpf/syscall.c:5767 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5765 [inline]
__x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5765
x64_sys_call+0x96b/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:322
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+0x77/0x7f

Uninit was stored to memory at:
bpf_bprintf_prepare+0x1393/0x23c0 kernel/bpf/helpers.c:1027
____bpf_snprintf kernel/bpf/helpers.c:1060 [inline]
bpf_snprintf+0x141/0x360 kernel/bpf/helpers.c:1044
___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
__bpf_prog_run288+0xb5/0xe0 kernel/bpf/core.c:2237
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
bpf_test_run+0x499/0xc30 net/bpf/test_run.c:425
bpf_prog_test_run_skb+0x14ea/0x1f20 net/bpf/test_run.c:1058
bpf_prog_test_run+0x6b7/0xad0 kernel/bpf/syscall.c:4269
__sys_bpf+0x6aa/0xd90 kernel/bpf/syscall.c:5678
__do_sys_bpf kernel/bpf/syscall.c:5767 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5765 [inline]
__x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5765
x64_sys_call+0x96b/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:322
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+0x77/0x7f

Local variable stack created at:
__bpf_prog_run288+0x45/0xe0 kernel/bpf/core.c:2237
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
bpf_test_run+0x499/0xc30 net/bpf/test_run.c:425

CPU: 1 PID: 5042 Comm: syz-executor235 Not tainted 6.9.0-syzkaller-02707-g614da38e2f7a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
=====================================================


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