linux-kernel - Re: Explanation on Uninitialized Variable bio in blk_rq_prep

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Message-ID: <Zv_-DSM2NhuiX3o2@kbusch-mbp>
Date: Fri, 4 Oct 2024 08:39:09 -0600
From: Keith Busch <kbusch@...nel.org>
To: SurajSonawane2415 <surajsonawane0215@...il.com>
Cc: hch@...radead.org, axboe@...nel.dk, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Explanation on Uninitialized Variable bio in blk_rq_prep_clone

On Fri, Oct 04, 2024 at 07:40:37PM +0530, SurajSonawane2415 wrote:
> In the function blk_rq_prep_clone, the variable bio is declared but can remain uninitialized 
> if the allocation with bio_alloc_clone fails. This can lead to undefined behavior when the 
> function attempts to free bio in the error handling section using bio_put(bio). 
> By initializing bio to NULL at declaration, we ensure that the cleanup code will only 
> interact with bio if it has been successfully allocated.

I don't think your explanation makes sense. The line where
bio_alloc_clone happens:

	bio = bio_alloc_clone(rq->q->disk->part0, bio_src, gfp_mask, bs);

If it fails, then bio is initialized to NULL.