Re: [PATCH] bcache: Fixup error handling in register_cache()

[Coly Li <colyli@suse.de>]

> 2023年10月4日 17:37，Jan Kara <jack@suse.cz> 写道：
> 
> Coverity has noticed that the printing of error message in
> register_cache() uses already freed bdev_handle to get to bdev. In fact
> the problem has been there even before commit "bcache: Convert to
> bdev_open_by_path()" just a bit more subtle one - cache object itself
> could have been freed by the time we looked at ca->bdev and we don't
> hold any reference to bdev either so even that could in principle go
> away (due to device unplug or similar). Fix all these problems by
> printing the error message before closing the bdev.
> 
> Fixes: dc893f51d24a ("bcache: Convert to bdev_open_by_path()")
> Signed-off-by: Jan Kara <jack@suse.cz>

Asked-by: Coly Li <colyli@suse.de <mailto:colyli@suse.de>>

Thanks.

Coly Li

> ---
> drivers/md/bcache/super.c | 23 ++++++++++-------------
> 1 file changed, 10 insertions(+), 13 deletions(-)
> 
> Hello Christian!
> 
> Can you please add this to patch to the bdev_handle conversion series? Either
> append it at the end of the series or just fold it into the bcache conversion.
> Whatever looks better for you.
> 
> 
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index c11ac86be72b..a30c8d4f2ac8 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -2354,6 +2354,13 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
> 
> ret = cache_alloc(ca);
> if (ret != 0) {
> + if (ret == -ENOMEM)
> + err = "cache_alloc(): -ENOMEM";
> + else if (ret == -EPERM)
> + err = "cache_alloc(): cache device is too small";
> + else
> + err = "cache_alloc(): unknown error";
> + pr_notice("error %pg: %s\n", bdev_handle->bdev, err);
> /*
> * If we failed here, it means ca->kobj is not initialized yet,
> * kobject_put() won't be called and there is no chance to
> @@ -2361,17 +2368,12 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
> * we explicitly call bdev_release() here.
> */
> bdev_release(bdev_handle);
> - if (ret == -ENOMEM)
> - err = "cache_alloc(): -ENOMEM";
> - else if (ret == -EPERM)
> - err = "cache_alloc(): cache device is too small";
> - else
> - err = "cache_alloc(): unknown error";
> - goto err;
> + return ret;
> }
> 
> if (kobject_add(&ca->kobj, bdev_kobj(bdev_handle->bdev), "bcache")) {
> - err = "error calling kobject_add";
> + pr_notice("error %pg: error calling kobject_add\n",
> +  bdev_handle->bdev);
> ret = -ENOMEM;
> goto out;
> }
> @@ -2389,11 +2391,6 @@ static int register_cache(struct cache_sb *sb, struct cache_sb_disk *sb_disk,
> 
> out:
> kobject_put(&ca->kobj);
> -
> -err:
> - if (err)
> - pr_notice("error %pg: %s\n", ca->bdev_handle->bdev, err);
> -
> return ret;
> }
> 
> -- 
> 2.35.3
>