Re: [PATCH 1/5] fs: ext4: initialize fsdata in pagecache_write()

Eric Biggers
2022-11-21T19:52:33Z

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@kernel.org>
> Fixes: c93d8f885809 ("ext4: add basic fs-verity support")
> Reported-by: syzbot+9767be679ef5016b6082@syzkaller.appspotmail.com
> Signed-off-by: Alexander Potapenko <glider@google.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@google.com>

- Eric