KCSAN: data-race in kcm_rfree / unreserve_rx_kcm

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: eeddbe68 Merge tag 's390-5.9-7' of git://git.kernel.org/pu..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1523f54b900000
kernel config: https://syzkaller.appspot.com/x/.config?x=1af5c6c89982088
dashboard link: https://syzkaller.appspot.com/bug?extid=f4c071abb34935866f72
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
CC: [and...@fb.com a...@kernel.org b...@vger.kernel.org dan...@iogearbox.net da...@davemloft.net edum...@google.com john.fa...@gmail.com ka...@fb.com kps...@chromium.org ku...@kernel.org linux-...@vger.kernel.org matthie...@tessares.net net...@vger.kernel.org songliu...@fb.com ste...@datenfreihafen.org y...@fb.com]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f4c071...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in kcm_rfree / unreserve_rx_kcm

write to 0xffff88809b4b13a0 of 8 bytes by task 3520 on cpu 0:
unreserve_rx_kcm+0x72/0x1e0 net/kcm/kcmsock.c:312
kcm_rcv_strparser+0x2d5/0x3d0 net/kcm/kcmsock.c:372
__strp_recv+0x699/0xf00 net/strparser/strparser.c:309
strp_recv+0x6d/0x80 net/strparser/strparser.c:343
tcp_read_sock+0x290/0xb10 net/ipv4/tcp.c:1646
strp_read_sock net/strparser/strparser.c:366 [inline]
do_strp_work net/strparser/strparser.c:414 [inline]
strp_work+0xd9/0x170 net/strparser/strparser.c:423
process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
kthread+0x20d/0x230 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff88809b4b13a0 of 8 bytes by task 14257 on cpu 1:
kcm_rfree+0xee/0x180 net/kcm/kcmsock.c:180
skb_release_head_state+0xb3/0x170 net/core/skbuff.c:651
skb_release_all net/core/skbuff.c:662 [inline]
__kfree_skb+0x14/0x150 net/core/skbuff.c:678
kfree_skb+0x53/0x190 net/core/skbuff.c:696
kcm_recvmsg+0x3c4/0x440 net/kcm/kcmsock.c:1160
____sys_recvmsg+0x15a/0x2e0 include/linux/uio.h:234
___sys_recvmsg net/socket.c:2618 [inline]
do_recvmmsg+0x35c/0xa30 net/socket.c:2716
__sys_recvmmsg net/socket.c:2795 [inline]
__do_sys_recvmmsg net/socket.c:2818 [inline]
__se_sys_recvmmsg net/socket.c:2811 [inline]
__x64_sys_recvmmsg+0xcc/0x150 net/socket.c:2811
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14257 Comm: syz-executor.2 Not tainted 5.9.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.