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BUG: KCSAN: data-race in p9_fd_create / p9_fd_create

read-write to 0xffff88816753d040 of 4 bytes by task 12198 on cpu 1:
 p9_fd_open net/9p/trans_fd.c:842 [inline]
 p9_fd_create+0x210/0x250 net/9p/trans_fd.c:1092
 p9_client_create+0x595/0xa70 net/9p/client.c:1011
 v9fs_session_init+0xf9/0xd80 fs/9p/v9fs.c:410
 v9fs_mount+0x69/0x640 fs/9p/vfs_super.c:123
 legacy_get_tree+0x74/0xd0 fs/fs_context.c:610
 vfs_get_tree+0x51/0x190 fs/super.c:1510
 do_new_mount+0x203/0x660 fs/namespace.c:3039
 path_mount+0x498/0xb40 fs/namespace.c:3369
 do_mount fs/namespace.c:3382 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount+0x27f/0x2d0 fs/namespace.c:3568
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read-write to 0xffff88816753d040 of 4 bytes by task 12200 on cpu 0:
 p9_fd_open net/9p/trans_fd.c:842 [inline]
 p9_fd_create+0x210/0x250 net/9p/trans_fd.c:1092
 p9_client_create+0x595/0xa70 net/9p/client.c:1011
 v9fs_session_init+0xf9/0xd80 fs/9p/v9fs.c:410
 v9fs_mount+0x69/0x640 fs/9p/vfs_super.c:123
 legacy_get_tree+0x74/0xd0 fs/fs_context.c:610
 vfs_get_tree+0x51/0x190 fs/super.c:1510
 do_new_mount+0x203/0x660 fs/namespace.c:3039
 path_mount+0x498/0xb40 fs/namespace.c:3369
 do_mount fs/namespace.c:3382 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount+0x27f/0x2d0 fs/namespace.c:3568
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000001 -> 0x00000801

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12200 Comm: syz-executor.4 Not tainted 6.4.0-rc6-syzkaller-00269-g1b29d271614a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
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