linux-kernel - [syzbot] [ext4?] KCSAN: data-race in __d_instantiate / lookup

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Date: Thu, 20 Jun 2024 01:23:22 -0700
From: syzbot <syzbot+5757df85a1c108693de1@...kaller.appspotmail.com>
To: adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, tytso@....edu
Subject: [syzbot] [ext4?] KCSAN: data-race in __d_instantiate / lookup_fast (7)

Hello,

syzbot found the following issue on:

HEAD commit:    e5b3efbe1ab1 Merge tag 'probes-fixes-v6.10-rc4' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f67fca980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=704451bc2941bcb0
dashboard link: https://syzkaller.appspot.com/bug?extid=5757df85a1c108693de1
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/aba434953b89/disk-e5b3efbe.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6c615db72106/vmlinux-e5b3efbe.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ec51cef20784/bzImage-e5b3efbe.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5757df85a1c108693de1@...kaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff8881207d1d80 of 4 bytes by task 25805 on cpu 1:
 __d_instantiate+0x2cd/0x3c0 fs/dcache.c:1855
 d_instantiate_new+0x5c/0xf0 fs/dcache.c:1899
 ext4_mkdir+0x5e6/0x740 fs/ext4/namei.c:3047
 vfs_mkdir+0x1f4/0x320 fs/namei.c:4131
 do_mkdirat+0x12f/0x2a0 fs/namei.c:4154
 __do_sys_mkdir fs/namei.c:4174 [inline]
 __se_sys_mkdir fs/namei.c:4172 [inline]
 __x64_sys_mkdir+0x44/0x50 fs/namei.c:4172
 x64_sys_call+0x10d4/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:84
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881207d1d80 of 4 bytes by task 25807 on cpu 0:
 d_revalidate fs/namei.c:860 [inline]
 lookup_fast+0xd9/0x2a0 fs/namei.c:1641
 walk_component fs/namei.c:2000 [inline]
 link_path_walk+0x403/0x810 fs/namei.c:2331
 path_lookupat+0x72/0x2b0 fs/namei.c:2492
 filename_lookup+0x127/0x300 fs/namei.c:2522
 user_path_at_empty+0x42/0x120 fs/namei.c:2929
 user_path_at include/linux/namei.h:58 [inline]
 path_setxattr+0x60/0x1a0 fs/xattr.c:666
 __do_sys_setxattr fs/xattr.c:687 [inline]
 __se_sys_setxattr fs/xattr.c:683 [inline]
 __x64_sys_setxattr+0x6d/0x80 fs/xattr.c:683
 x64_sys_call+0x2957/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:189
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00280040

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 25807 Comm: syz-executor.4 Tainted: G        W          6.10.0-rc4-syzkaller-00052-ge5b3efbe1ab1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
==================================================================


---
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