[moderation] [trace?] [bpf?] KCSAN: data-race in memcpy_and_pad / prepare_signal

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f975f08c2e89 Merge tag 'for-6.17-rc6-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=131cd858580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=f93991205b06cd3a656f
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [and...@kernel.org a...@kernel.org b...@vger.kernel.org dan...@iogearbox.net edd...@gmail.com hao...@google.com john.fa...@gmail.com jo...@kernel.org kps...@kernel.org linux-...@vger.kernel.org linux-tra...@vger.kernel.org marti...@linux.dev mathieu....@efficios.com mattbo...@google.com mhir...@kernel.org ros...@goodmis.org s...@fomichev.me so...@kernel.org yongho...@linux.dev]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/40093482f336/disk-f975f08c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1f0904982798/vmlinux-f975f08c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3bdb3220239d/bzImage-f975f08c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f93991...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in memcpy_and_pad / prepare_signal

read-write to 0xffff88811a832638 of 8 bytes by interrupt on cpu 1:
task_clear_jobctl_pending kernel/signal.c:339 [inline]
prepare_signal+0x21d/0x670 kernel/signal.c:901
__send_signal_locked+0x30/0x760 kernel/signal.c:1053
send_signal_locked+0x34e/0x3c0 kernel/signal.c:1216
do_send_sig_info+0x9f/0xf0 kernel/signal.c:1269
group_send_sig_info+0x6f/0x90 kernel/signal.c:1419
do_bpf_send_signal+0x64/0xf0 kernel/trace/bpf_trace.c:814
irq_work_single kernel/irq_work.c:221 [inline]
irq_work_run_list kernel/irq_work.c:252 [inline]
irq_work_run+0xe2/0x2d0 kernel/irq_work.c:261
__sysvec_irq_work+0x22/0x170 arch/x86/kernel/irq_work.c:22
instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
sysvec_irq_work+0x66/0x80 arch/x86/kernel/irq_work.c:17
asm_sysvec_irq_work+0x1a/0x20 arch/x86/include/asm/idtentry.h:738
__wrmsrq arch/x86/include/asm/msr.h:80 [inline]
native_write_msr arch/x86/include/asm/msr.h:137 [inline]
wrmsrq arch/x86/include/asm/msr.h:199 [inline]
native_apic_msr_write+0x3d/0x60 arch/x86/include/asm/apic.h:212
apic_write arch/x86/include/asm/apic.h:405 [inline]
x2apic_send_IPI_self+0x10/0x20 arch/x86/kernel/apic/x2apic_phys.c:107
__apic_send_IPI_self arch/x86/include/asm/apic.h:455 [inline]
arch_irq_work_raise+0x46/0x50 arch/x86/kernel/irq_work.c:31
irq_work_raise kernel/irq_work.c:84 [inline]
__irq_work_queue_local+0x10f/0x2c0 kernel/irq_work.c:112
irq_work_queue+0x70/0x100 kernel/irq_work.c:124
bpf_send_signal_common+0x280/0x300 kernel/trace/bpf_trace.c:872
____bpf_send_signal kernel/trace/bpf_trace.c:881 [inline]
bpf_send_signal+0x1d/0x30 kernel/trace/bpf_trace.c:879
bpf_prog_631417f49dd64198+0x25/0x4c
bpf_dispatcher_nop_func include/linux/bpf.h:1332 [inline]
__bpf_prog_run include/linux/filter.h:718 [inline]
bpf_prog_run include/linux/filter.h:725 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2257 [inline]
bpf_trace_run2+0x104/0x1c0 kernel/trace/bpf_trace.c:2298
__traceiter_kfree+0x2e/0x50 include/trace/events/kmem.h:94
__do_trace_kfree include/trace/events/kmem.h:94 [inline]
trace_kfree include/trace/events/kmem.h:94 [inline]
kfree+0x27b/0x320 mm/slub.c:4881
___sys_recvmsg+0x135/0x370 net/socket.c:2877
do_recvmmsg+0x1ef/0x540 net/socket.c:2971
__sys_recvmmsg net/socket.c:3045 [inline]
__do_sys_recvmmsg net/socket.c:3068 [inline]
__se_sys_recvmmsg net/socket.c:3061 [inline]
__x64_sys_recvmmsg+0xe5/0x170 net/socket.c:3061
x64_sys_call+0x27a6/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:300
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811a832100 of 3264 bytes by task 24448 on cpu 0:
memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1007
arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:98
dup_task_struct+0x83/0x6a0 kernel/fork.c:877
copy_process+0x399/0x2000 kernel/fork.c:2004
kernel_clone+0x16c/0x5c0 kernel/fork.c:2605
__do_sys_clone3 kernel/fork.c:2909 [inline]
__se_sys_clone3+0x1c2/0x200 kernel/fork.c:2888
__x64_sys_clone3+0x31/0x40 kernel/fork.c:2888
x64_sys_call+0x1fc9/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:436
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 24448 Comm: syz.2.7199 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================


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