linux-kernel - Re: [syzbot] [mm?] KCSAN: data-race in generic_fillattr / shmem

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Message-ID: <000000000000cb63e20621950e5f@google.com>
Date: Sat, 07 Sep 2024 22:39:02 -0700
From: syzbot <syzbot+702361cf7e3d95758761@...kaller.appspotmail.com>
To: aha310510@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] KCSAN: data-race in generic_fillattr / shmem_mknod (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KCSAN: data-race in ext4_free_inodes_count / ext4_free_inodes_set

==================================================================
BUG: KCSAN: data-race in ext4_free_inodes_count / ext4_free_inodes_set

write to 0xffff888103fc500e of 2 bytes by task 13551 on cpu 0:
 ext4_free_inodes_set+0x1f/0x80 fs/ext4/super.c:405
 __ext4_new_inode+0x15ca/0x2200 fs/ext4/ialloc.c:1216
 ext4_symlink+0x242/0x5a0 fs/ext4/namei.c:3391
 vfs_symlink+0xca/0x1d0 fs/namei.c:4568
 do_symlinkat+0xe3/0x340 fs/namei.c:4594
 __do_sys_symlinkat fs/namei.c:4610 [inline]
 __se_sys_symlinkat fs/namei.c:4607 [inline]
 __x64_sys_symlinkat+0x5e/0x70 fs/namei.c:4607
 x64_sys_call+0x1dda/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:267
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x54/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

read to 0xffff888103fc500e of 2 bytes by task 13552 on cpu 1:
 ext4_free_inodes_count+0x1c/0x80 fs/ext4/super.c:349
 find_group_other fs/ext4/ialloc.c:594 [inline]
 __ext4_new_inode+0x6ec/0x2200 fs/ext4/ialloc.c:1017
 ext4_symlink+0x242/0x5a0 fs/ext4/namei.c:3391
 vfs_symlink+0xca/0x1d0 fs/namei.c:4568
 do_symlinkat+0xe3/0x340 fs/namei.c:4594
 __do_sys_symlinkat fs/namei.c:4610 [inline]
 __se_sys_symlinkat fs/namei.c:4607 [inline]
 __x64_sys_symlinkat+0x5e/0x70 fs/namei.c:4607
 x64_sys_call+0x1dda/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:267
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x54/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

value changed: 0x185c -> 0x185b

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13552 Comm: syz-executor.1 Not tainted 6.11.0-rc6-syzkaller-00326-gd1f2d51b711a-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
==================================================================


Tested on:

commit:         d1f2d51b Merge tag 'clk-fixes-for-linus' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17ffef29980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e81d40b0108ea8fe
dashboard link: https://syzkaller.appspot.com/bug?extid=702361cf7e3d95758761
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17d10e00580000