Subject: [syzbot] [net?] [v9fs?] KCSAN: data-race in p9_fd_create / p9_fd_create (2)

From: syzbot <[email-masked]>
Date: Tue, 29 Aug 2023 02:39:53 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    53663f4103ff Merge tag 'nfs-for-6.5-2' of git://git.linux-..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=103fc55fa80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f12c32a009b80107
dashboard link: https://syzkaller.appspot.com/bug?extid=e441aeeb422763cc5511
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f32101f0e8a2/disk-53663f41.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2e577e9d7daf/vmlinux-53663f41.xz
kernel image: https://storage.googleapis.com/syzbot-assets/af8ae7d4d06e/bzImage-53663f41.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KCSAN: data-race in p9_fd_create / p9_fd_create

read-write to 0xffff888130fb3d48 of 4 bytes by task 15599 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:1010
 v9fs_session_init+0xf9/0xd90 fs/9p/v9fs.c:410
 v9fs_mount+0x69/0x630 fs/9p/vfs_super.c:123
 legacy_get_tree+0x74/0xd0 fs/fs_context.c:611
 vfs_get_tree+0x51/0x190 fs/super.c:1519
 do_new_mount+0x203/0x660 fs/namespace.c:3335
 path_mount+0x496/0xb30 fs/namespace.c:3662
 do_mount fs/namespace.c:3675 [inline]
 __do_sys_mount fs/namespace.c:3884 [inline]
 __se_sys_mount+0x27f/0x2d0 fs/namespace.c:3861
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3861
 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 0xffff888130fb3d48 of 4 bytes by task 15563 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:1010
 v9fs_session_init+0xf9/0xd90 fs/9p/v9fs.c:410
 v9fs_mount+0x69/0x630 fs/9p/vfs_super.c:123
 legacy_get_tree+0x74/0xd0 fs/fs_context.c:611
 vfs_get_tree+0x51/0x190 fs/super.c:1519
 do_new_mount+0x203/0x660 fs/namespace.c:3335
 path_mount+0x496/0xb30 fs/namespace.c:3662
 do_mount fs/namespace.c:3675 [inline]
 __do_sys_mount fs/namespace.c:3884 [inline]
 __se_sys_mount+0x27f/0x2d0 fs/namespace.c:3861
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3861
 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: 0x00008002 -> 0x00008802

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15563 Comm: syz-executor.3 Not tainted 6.5.0-rc7-syzkaller-00013-g53663f4103ff #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
==================================================================

---
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