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SubjectRe: [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@samsung.com>

Reviewed-by: Gu Zheng <guz.fnst@cn.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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