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BUG: KCSAN: data-race in fifo_open / wait_for_partner

read-write to 0xffff88810def1970 of 4 bytes by task 27707 on cpu 0:
 fifo_open+0x9c/0x5d0 fs/pipe.c:1086
 do_dentry_open+0x520/0x870 fs/open.c:817
 vfs_open+0x43/0x50 fs/open.c:931
 do_open fs/namei.c:3254 [inline]
 path_openat+0x1844/0x20a0 fs/namei.c:3371
 do_filp_open+0xbd/0x1d0 fs/namei.c:3398
 do_sys_openat2+0xa3/0x240 fs/open.c:1172
 do_sys_open fs/open.c:1188 [inline]
 __do_sys_openat fs/open.c:1204 [inline]
 __se_sys_openat fs/open.c:1199 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1199
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810def1970 of 4 bytes by task 27715 on cpu 1:
 pipe_unlock fs/pipe.c:80 [inline]
 wait_for_partner+0x98/0x1d0 fs/pipe.c:1060
 fifo_open+0x47f/0x5d0 fs/pipe.c:1130
 do_dentry_open+0x520/0x870 fs/open.c:817
 vfs_open+0x43/0x50 fs/open.c:931
 do_open fs/namei.c:3254 [inline]
 path_openat+0x1844/0x20a0 fs/namei.c:3371
 do_filp_open+0xbd/0x1d0 fs/namei.c:3398
 do_sys_openat2+0xa3/0x240 fs/open.c:1172
 do_sys_open fs/open.c:1188 [inline]
 __do_sys_open fs/open.c:1196 [inline]
 __se_sys_open fs/open.c:1192 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1192
 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: 27715 Comm: syz-executor.1 Not tainted 5.11.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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