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Date: Mon, 7 Jul 2014 09:58:45 +0800
From: Gu Zheng <guz.fnst@...fujitsu.com>
To: Chao Yu <chao2.yu@...sung.com>
CC: Jaegeuk Kim <jaegeuk@...nel.org>,
Changman Lee <cm224.lee@...sung.com>,
<linux-f2fs-devel@...ts.sourceforge.net>,
<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [f2fs-dev][PATCH] f2fs: avoid to access NULL pointer in issue_flush_thread
Hi Yu,
Thanks for your catch.
Regards,
Gu
On 07/07/2014 09:39 AM, Chao Yu wrote:
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=75861
>
> Denis 2014-05-10 11:28:59 UTC reported:
> "F2FS-fs (mmcblk0p28): mounting..
> Unable to handle kernel NULL pointer dereference at virtual address 00000018
> ...
> [<c0a2f678>] (_raw_spin_lock+0x3c/0x70) from [<c03a0330>] (issue_flush_thread+0x50/0x17c)
> [<c03a0330>] (issue_flush_thread+0x50/0x17c) from [<c01b4064>] (kthread+0x98/0xa4)
> [<c01b4064>] (kthread+0x98/0xa4) from [<c0108060>] (kernel_thread_exit+0x0/0x8)"
>
> This patch assign cmd_control_info in sm_info before issue_flush_thread is being
> created, so this make sure that issue flush thread will have no chance to access
> invalid info in fcc.
>
> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
Reviewed-by: Gu Zheng <guz.fnst@...fujitsu.com>
> ---
> fs/f2fs/segment.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index bb5980d..a4f8375 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -272,14 +272,15 @@ int create_flush_cmd_control(struct f2fs_sb_info *sbi)
> return -ENOMEM;
> spin_lock_init(&fcc->issue_lock);
> init_waitqueue_head(&fcc->flush_wait_queue);
> + sbi->sm_info->cmd_control_info = fcc;
> fcc->f2fs_issue_flush = kthread_run(issue_flush_thread, sbi,
> "f2fs_flush-%u:%u", MAJOR(dev), MINOR(dev));
> if (IS_ERR(fcc->f2fs_issue_flush)) {
> err = PTR_ERR(fcc->f2fs_issue_flush);
> kfree(fcc);
> + sbi->sm_info->cmd_control_info = NULL;
> return err;
> }
> - sbi->sm_info->cmd_control_info = fcc;
>
> return err;
> }
--
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