On Sat, Feb 26, 2022 at 11:17:48PM +0100, Niels Dossche wrote:
> Prevent bio_list from changing in the while loop condition such that the
> body of the loop won't execute with a potentially NULL pointer for
> bio_list, which causes a NULL dereference later on.
Is this something you've seen happen, or something you think might
happen?
> Signed-off-by: Niels Dossche <dossche.niels@xxxxxxxxx>
> ---
> fs/direct-io.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 654443558047..806f05407019 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -545,19 +545,22 @@ static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
> int ret = 0;
>
> if (sdio->reap_counter++ >= 64) {
> + unsigned long flags;
> +
> + spin_lock_irqsave(&dio->bio_lock, flags);
> while (dio->bio_list) {
> - unsigned long flags;
> struct bio *bio;
> int ret2;
>
> - spin_lock_irqsave(&dio->bio_lock, flags);
> bio = dio->bio_list;
> dio->bio_list = bio->bi_private;
> spin_unlock_irqrestore(&dio->bio_lock, flags);
> ret2 = blk_status_to_errno(dio_bio_complete(dio, bio));
> if (ret == 0)
> ret = ret2;
> + spin_lock_irqsave(&dio->bio_lock, flags);
> }
> + spin_unlock_irqrestore(&dio->bio_lock, flags);
> sdio->reap_counter = 0;
> }
> return ret;
> --
> 2.35.1
>
