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From: Chao Yu <chao@kernel.org>
To: Wenjie Qi <qwjhust@gmail.com>, jaegeuk@kernel.org
Cc: chao@kernel.org, stable@kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-kernel@vger.kernel.org, qiwenjie@xiaomi.com
Subject: Re: [PATCH v4 1/2] f2fs: avoid NULL checkpoint thread access in sysfs
Date: Tue, 4 Aug 2026 10:55:46 +0800	[thread overview]
Message-ID: <81d7efa2-8e60-4f92-9cf0-613f6116756c@kernel.org> (raw)
In-Reply-To: <20260804014849.1942326-1-qiwenjie@xiaomi.com>

On 8/4/26 09:48, Wenjie Qi wrote:
> checkpoint_merge can be enabled even when no checkpoint merge thread is
> running. A read-only mount is one case: f2fs does not start
> f2fs_issue_ckpt there, but ckpt_thread_ioprio is still writable through
> sysfs.
> 
> The ckpt_thread_ioprio store path updates the saved ioprio value and,
> when checkpoint_merge is enabled, calls set_task_ioprio() for the
> checkpoint thread. If cprc->f2fs_issue_ckpt is NULL, that dereferences a
> NULL task pointer.
> 
> Protect ckpt_thread_ioprio sysfs writes with s_umount as well, so the
> checkpoint thread cannot disappear under the store path while updating
> its ioprio.
> 
> Fixes: e65920661708 ("f2fs: add ckpt_thread_ioprio sysfs node")
> Cc: stable@kernel.org
> Signed-off-by: Wenjie Qi <qiwenjie@xiaomi.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,

  parent reply	other threads:[~2026-08-04  2:55 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-04  1:48 Wenjie Qi
2026-08-04  1:48 ` [PATCH v4 2/2] f2fs: protect critical_task_priority updates with s_umount Wenjie Qi
2026-08-04  2:56   ` Chao Yu
2026-08-04  2:55 ` Chao Yu [this message]
2026-08-05 21:20 ` [f2fs-dev] [PATCH v4 1/2] f2fs: avoid NULL checkpoint thread access in sysfs patchwork-bot+f2fs

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