linux-ext4 - Re: More KCSAN data-race Reports

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Date:   Mon, 12 Apr 2021 11:02:12 +0200
From:   Jan Kara <jack@...e.cz>
To:     Hao Sun <sunhao.th@...il.com>
Cc:     linux-kernel@...r.kernel.org, jack@...e.com,
        linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: More KCSAN data-race Reports

Hello,

On Sun 11-04-21 11:42:05, Hao Sun wrote:
> Since the last KCSAN report[1], I found two more KCSAN reports that
> Syzbot had not reported.
> Not sure if they are valid bugs, I hope the stack information in
> reports can help you locate the problem.
> Kernel config can be found in the attachment.

Do we have symbolic decoding of the traces below? Because involved
functions are really big so it's difficult to guess what KCSAN is
complaining about... At least I wasn't able to guess it after looking into
the stacktraces for a while.

								Honza

> 
> Here is the detailed information:
> commit:   3b9cdafb5358eb9f3790de2f728f765fef100731
> version:   linux 5.11
> git tree:    upstream
> 
> Report-1
> ==================================================================
> BUG: KCSAN: data-race in ext4_mark_iloc_dirty / jbd2_journal_commit_transaction
> 
> read-write to 0xffff88804451d800 of 8 bytes by task 4821 on cpu 1:
>  jbd2_journal_commit_transaction+0x222/0x3200
>  kjournald2+0x253/0x470
>  kthread+0x1f0/0x220
>  ret_from_fork+0x1f/0x30
> 
> read to 0xffff88804451d800 of 8 bytes by task 8418 on cpu 0:
>  ext4_mark_iloc_dirty+0x14ec/0x16e0
>  __ext4_mark_inode_dirty+0x4d2/0x5d0
>  ext4_evict_inode+0xb9f/0xed0
>  evict+0x1a6/0x410
>  iput+0x3fc/0x510
>  do_unlinkat+0x2c9/0x4d0
>  __x64_sys_unlink+0x2c/0x30
>  do_syscall_64+0x39/0x80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Report-2
> ==================================================================
> BUG: KCSAN: data-race in __ext4_handle_dirty_metadata /
> jbd2_journal_commit_transaction
> 
> read-write to 0xffff88800e142800 of 8 bytes by task 4823 on cpu 0:
>  jbd2_journal_commit_transaction+0x222/0x3200
>  kjournald2+0x253/0x470
>  kthread+0x1f0/0x220
>  ret_from_fork+0x1f/0x30
> 
> read to 0xffff88800e142800 of 8 bytes by task 7925 on cpu 1:
>  __ext4_handle_dirty_metadata+0x11a/0x590
>  ext4_mark_iloc_dirty+0x12dd/0x16e0
>  __ext4_mark_inode_dirty+0x4d2/0x5d0
>  ext4_dirty_inode+0x86/0xa0
>  __mark_inode_dirty+0x70/0x6b0
>  file_update_time+0x3ab/0x3f0
>  file_modified+0x62/0x80
>  ext4_buffered_write_iter+0x1f9/0x3d0
>  ext4_file_write_iter+0x45e/0x10d0
>  vfs_write+0x6db/0x7c0
>  ksys_write+0xce/0x180
>  __x64_sys_write+0x3e/0x50
>  do_syscall_64+0x39/0x80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> 
> [1] https://lore.kernel.org/lkml/CACkBjsZW5Sp4jB51+C5mrMssgq73x8iEko_EV6CTXVvtVa7KPQ@mail.gmail.com/


-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR