linux-kernel - Re: [PATCH] scsi: fix uninitialized pointers with free attr

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Message-ID: <f7f26ae6-31d7-4793-8daa-331622460833@suswa.mountain>
Date: Thu, 6 Nov 2025 17:46:54 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: James Bottomley <James.Bottomley@...senpartnership.com>
Cc: Ally Heev <allyheev@...il.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: fix uninitialized pointers with free attr

On Wed, Nov 05, 2025 at 10:32:19AM -0500, James Bottomley wrote:
> > > > diff --git a/drivers/scsi/scsi_debug.c
> > > > b/drivers/scsi/scsi_debug.c
> > > > index
> > > > b2ab97be5db3d43d5a5647968623b8db72448379..89b36d65926bdd15c0ae93a
> > > > 6bd2
> > > > ea968e25c0e74 100644
> > > > --- a/drivers/scsi/scsi_debug.c
> > > > +++ b/drivers/scsi/scsi_debug.c
> > > > @@ -2961,11 +2961,11 @@ static int resp_mode_sense(struct
> > > > scsi_cmnd
> > > > *scp,
> > > >  	int target_dev_id;
> > > >  	int target = scp->device->id;
> > > >  	unsigned char *ap;
> > > > -	unsigned char *arr __free(kfree);
> > > >  	unsigned char *cmd = scp->cmnd;
> > > >  	bool dbd, llbaa, msense_6, is_disk, is_zbc, is_tape;
> > > >  
> > > > -	arr = kzalloc(SDEBUG_MAX_MSENSE_SZ, GFP_ATOMIC);
> > > > +	unsigned char *arr __free(kfree) =
> > > > kzalloc(SDEBUG_MAX_MSENSE_SZ, GFP_ATOMIC);
> > > > +
> > > 
> > > Moving variable assignments inside code makes it way harder to
> > > read. Given that compilers will eventually detect if we do a return
> > > before initialization, can't you have smatch do the same rather
> > > than trying to force something like this?
> > 
> > This isn't a Smatch thing, it's a change to checkpatch.
> > 
> > (Smatch does work as you describe).
> 
> So why are we bothering with something like this in checkpatch if we
> can detect the true problem condition and we expect compilers to catch
> up?  Encouraging people to write code like the above isn't in anyone's
> best interest.

Initializing __free variables has been considered best practice for a
long time.  Reviewers often will complain even if it doesn't cause a
bug.

regards,
dan carpenter