LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Eric Biggers <ebiggers@kernel.org>
To: Chao Yu <yuchao0@huawei.com>
Cc: jaegeuk@kernel.org, linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [PATCH 3/4] f2fs: fix NULL pointer dereference in f2fs_verity_work()
Date: Fri, 20 Mar 2020 12:11:49 -0700	[thread overview]
Message-ID: <20200320191149.GL851@sol.localdomain> (raw)
In-Reply-To: <20200319115800.108926-3-yuchao0@huawei.com>

On Thu, Mar 19, 2020 at 07:57:59PM +0800, Chao Yu wrote:
> If both compression and fsverity feature is on, generic/572 will
> report below NULL pointer dereference bug.
> 
>  BUG: kernel NULL pointer dereference, address: 0000000000000018
>  RIP: 0010:f2fs_verity_work+0x60/0x90 [f2fs]
>  #PF: supervisor read access in kernel mode
>  Workqueue: fsverity_read_queue f2fs_verity_work [f2fs]
>  RIP: 0010:f2fs_verity_work+0x60/0x90 [f2fs]
>  Call Trace:
>   process_one_work+0x16c/0x3f0
>   worker_thread+0x4c/0x440
>   ? rescuer_thread+0x350/0x350
>   kthread+0xf8/0x130
>   ? kthread_unpark+0x70/0x70
>   ret_from_fork+0x35/0x40
> 
> There are two issue in f2fs_verity_work():
> - it needs to traverse and verify all pages in bio.
> - if pages in bio belong to non-compressed cluster, accessing
> decompress IO context stored in page private will cause NULL
> pointer dereference.
> 
> Fix them.
> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
>  fs/f2fs/data.c | 35 ++++++++++++++++++++++++++++++-----
>  1 file changed, 30 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 5c5db09324b7..66e49fc1056e 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -187,12 +187,37 @@ static void f2fs_verify_pages(struct page **rpages, unsigned int cluster_size)
>  
>  static void f2fs_verify_bio(struct bio *bio)
>  {
> -	struct page *page = bio_first_page_all(bio);
> -	struct decompress_io_ctx *dic =
> -			(struct decompress_io_ctx *)page_private(page);
> +	struct bio_vec *bv;
> +	struct bvec_iter_all iter_all;
> +	struct decompress_io_ctx *dic, *pdic = NULL;
> +
> +	bio_for_each_segment_all(bv, bio, iter_all) {
> +		struct page *page = bv->bv_page;
> +
> +		dic = (struct decompress_io_ctx *)page_private(page);
> +
> +		if (dic) {
> +			if (dic != pdic) {
> +				f2fs_verify_pages(dic->rpages,
> +							dic->cluster_size);
> +				f2fs_free_dic(dic);
> +				pdic = dic;
> +			}
> +			continue;
> +		}
> +		pdic = dic;
>  
> -	f2fs_verify_pages(dic->rpages, dic->cluster_size);
> -	f2fs_free_dic(dic);
> +		if (bio->bi_status || PageError(page)) {
> +			ClearPageUptodate(page);
> +			ClearPageError(page);
> +		} else {
> +			if (fsverity_verify_page(page))
> +				SetPageUptodate(page);
> +			else
> +				SetPageError(page);
> +		}
> +		unlock_page(page);
> +	}

I'm a bit confused why you added SetPageError() before unlocking the page.
The other error paths actually clear the Error flag, not set it.  I thought
there's a reason for that?

- Eric

  reply	other threads:[~2020-03-20 19:11 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-19 11:57 [PATCH 1/4] f2fs: fix to avoid potential deadlock Chao Yu
2020-03-19 11:57 ` [PATCH 2/4] f2fs: don't trigger data flush in foreground operation Chao Yu
2020-03-19 11:57 ` [PATCH 3/4] f2fs: fix NULL pointer dereference in f2fs_verity_work() Chao Yu
2020-03-20 19:11   ` Eric Biggers [this message]
2020-03-21 12:16     ` [f2fs-dev] " Chao Yu
2020-03-19 11:58 ` [PATCH 4/4] f2fs: fix NULL pointer dereference in f2fs_write_begin() Chao Yu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200320191149.GL851@sol.localdomain \
    --to=ebiggers@kernel.org \
    --cc=jaegeuk@kernel.org \
    --cc=linux-f2fs-devel@lists.sourceforge.net \
    --cc=linux-kernel@vger.kernel.org \
    --cc=yuchao0@huawei.com \
    --subject='Re: [PATCH 3/4] f2fs: fix NULL pointer dereference in f2fs_verity_work()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).