[moderation] [serial?] KCSAN: data-race in serial8250_do_startup / serial8250_handle_irq (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fee3e843b309 Merge tag 'bcachefs-2025-05-15' of git://evil..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=121a42d4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7bf27d52ff5e6b29
dashboard link: https://syzkaller.appspot.com/bug?extid=953ec234fc6a0aac85e1
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
CC: [gre...@linuxfoundation.org jiri...@kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c93be4cd4778/disk-fee3e843.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/72f48a176354/vmlinux-fee3e843.xz
kernel image: https://storage.googleapis.com/syzbot-assets/795a5e6b7b34/bzImage-fee3e843.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+953ec2...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in serial8250_do_startup / serial8250_handle_irq

write to 0xffffffff88e91976 of 1 bytes by task 6187 on cpu 1:
serial8250_do_startup+0x1661/0x1eb0 drivers/tty/serial/8250/8250_port.c:2464
serial8250_startup+0x41/0x50 drivers/tty/serial/8250/8250_port.c:2486
uart_port_startup drivers/tty/serial/serial_core.c:323 [inline]
uart_startup+0x466/0x930 drivers/tty/serial/serial_core.c:367
uart_port_activate+0x67/0xc0 drivers/tty/serial/serial_core.c:1994
tty_port_open+0x148/0x1d0 drivers/tty/tty_port.c:784
uart_open+0x30/0x40 drivers/tty/serial/serial_core.c:1974
tty_open+0x3d1/0xaf0 drivers/tty/tty_io.c:2146
chrdev_open+0x2e8/0x3a0 fs/char_dev.c:414
do_dentry_open+0x646/0xa20 fs/open.c:956
vfs_open+0x37/0x1e0 fs/open.c:1086
do_open fs/namei.c:3880 [inline]
path_openat+0x1c5e/0x2170 fs/namei.c:4039
do_filp_open+0x109/0x230 fs/namei.c:4066
do_sys_openat2+0xa6/0x110 fs/open.c:1429
do_sys_open fs/open.c:1444 [inline]
__do_sys_openat fs/open.c:1460 [inline]
__se_sys_openat fs/open.c:1455 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1455
x64_sys_call+0x1af/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88e91976 of 1 bytes by interrupt on cpu 0:
serial8250_handle_irq+0x3f9/0x660 drivers/tty/serial/8250/8250_port.c:1948
serial8250_default_handle_irq+0x8e/0x120 drivers/tty/serial/8250/8250_port.c:1970
serial8250_interrupt+0x60/0x110 drivers/tty/serial/8250/8250_core.c:86
__handle_irq_event_percpu+0x90/0x440 kernel/irq/handle.c:158
handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
handle_irq_event+0x64/0xf0 kernel/irq/handle.c:210
handle_edge_irq+0x1d0/0x5d0 kernel/irq/chip.c:831
generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
handle_irq arch/x86/kernel/irq.c:254 [inline]
call_irq_handler arch/x86/kernel/irq.c:266 [inline]
__common_interrupt+0x60/0x100 arch/x86/kernel/irq.c:292
common_interrupt+0x7e/0x90 arch/x86/kernel/irq.c:285
asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
check_kcov_mode kernel/kcov.c:185 [inline]
__sanitizer_cov_trace_pc+0x37/0x70 kernel/kcov.c:217
__skb_datagram_iter+0x469/0x680 net/core/datagram.c:414
skb_copy_datagram_iter+0x3d/0x110 net/core/datagram.c:538
skb_copy_datagram_msg include/linux/skbuff.h:4128 [inline]
__unix_dgram_recvmsg+0x4df/0x840 net/unix/af_unix.c:2464
unix_dgram_recvmsg+0x81/0x90 net/unix/af_unix.c:2522
sock_recvmsg_nosec+0x107/0x130 net/socket.c:1017
____sys_recvmsg+0x26f/0x280 net/socket.c:2784
___sys_recvmsg+0x11f/0x370 net/socket.c:2828
do_recvmmsg+0x1ef/0x540 net/socket.c:2923
__sys_recvmmsg net/socket.c:2997 [inline]
__do_sys_recvmmsg net/socket.c:3020 [inline]
__se_sys_recvmmsg net/socket.c:3013 [inline]
__x64_sys_recvmmsg+0xe5/0x170 net/socket.c:3013
x64_sys_call+0x1c6a/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:300
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00 -> 0x05

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6177 Comm: syz.1.814 Not tainted 6.15.0-rc6-syzkaller-00188-gfee3e843b309 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
==================================================================


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