linux-ext4 - Re: [PATCH 1/5] fs: ext4: initialize fsdata in pagecache

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Date:   Mon, 21 Nov 2022 19:52:21 +0000
From:   Eric Biggers <ebiggers@...nel.org>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        tytso@....edu, adilger.kernel@...ger.ca, jaegeuk@...nel.org,
        chao@...nel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        syzbot+9767be679ef5016b6082@...kaller.appspotmail.com
Subject: Re: [PATCH 1/5] fs: ext4: initialize fsdata in pagecache_write()

On Mon, Nov 21, 2022 at 12:21:30PM +0100, Alexander Potapenko wrote:
> When aops->write_begin() does not initialize fsdata, KMSAN reports
> an error passing the latter to aops->write_end().
> 
> Fix this by unconditionally initializing fsdata.
> 
> Cc: Eric Biggers <ebiggers@...nel.org>
> Fixes: c93d8f885809 ("ext4: add basic fs-verity support")
> Reported-by: syzbot+9767be679ef5016b6082@...kaller.appspotmail.com
> Signed-off-by: Alexander Potapenko <glider@...gle.com>
> ---
>  fs/ext4/verity.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c
> index 3c640bd7ecaeb..30e3b65798b50 100644
> --- a/fs/ext4/verity.c
> +++ b/fs/ext4/verity.c
> @@ -79,7 +79,7 @@ static int pagecache_write(struct inode *inode, const void *buf, size_t count,
>  		size_t n = min_t(size_t, count,
>  				 PAGE_SIZE - offset_in_page(pos));
>  		struct page *page;
> -		void *fsdata;
> +		void *fsdata = NULL;
>  		int res;
>  
>  		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);

Reviewed-by: Eric Biggers <ebiggers@...gle.com>

- Eric