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From: "zhangyi (F)" <yi.zhang@huawei.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: <linux-ext4@vger.kernel.org>, <jack@suse.cz>, <adilger.kernel@dilger.ca>
Subject: Re: [PATCH v5] ext4: fix potential use after free in system zone via remount with noblock_validity
Date: Mon, 26 Aug 2019 16:31:41 +0800	[thread overview]
Message-ID: <33767946-1e6f-5165-94b3-46e2da15172f@huawei.com> (raw)
In-Reply-To: <20190826025612.GB4918@mit.edu>

On 2019/8/26 10:56, Theodore Y. Ts'o Wrote:
> I added a missing rcu_read_lock() to prevent a suspicious RCU
> warning when CONFIG_PROVE_RCU is enabled:
> 
> diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
> index 003dc1dc2da3..f7bc914a74df 100644
> --- a/fs/ext4/block_validity.c
> +++ b/fs/ext4/block_validity.c
> @@ -330,11 +330,13 @@ void ext4_release_system_zone(struct super_block *sb)
>  {
>  	struct ext4_system_blocks *system_blks;
>  
> +	rcu_read_lock();
>  	system_blks = rcu_dereference(EXT4_SB(sb)->system_blks);
>  	rcu_assign_pointer(EXT4_SB(sb)->system_blks, NULL);
>  
>  	if (system_blks)
>  		call_rcu(&system_blks->rcu, ext4_destroy_system_zone);
> +	rcu_read_unlock();
>  }
>  
>  int ext4_data_block_valid(struct ext4_sb_info *sbi, ext4_fsblk_t start_blk,
> 

Hi Ted，
Sorry about missing this warning, I think switch to use:
  system_blks = rcu_dereference_raw(EXT4_SB(sb)->system_blks);
or
  system_blks = rcu_dereference_protected(EXT4_SB(sb)->system_blks, true);
is enough to fix this waring, am I missing something?

Thanks,
Yi.


  reply	other threads:[~2019-08-26  8:31 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-15 11:47 [PATCH v5] ext4: fix potential use after free in system zone via remount with noblock_validity zhangyi (F)
2019-08-25  3:40 ` Theodore Y. Ts'o
2019-08-25 17:32   ` Eric Biggers
2019-08-26  2:56   ` Theodore Y. Ts'o
2019-08-26  8:31     ` zhangyi (F) [this message]
2019-08-26 15:03       ` Jan Kara
2019-08-27  9:20         ` zhangyi (F)

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