linux-kernel - Re: [PATCH] ext4: fix memory leak in ext4_fill

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Date:   Thu, 29 Apr 2021 23:44:32 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     Vegard Nossum <vegard.nossum@...cle.com>,
        akpm@...ux-foundation.org, peterz@...radead.org, axboe@...nel.dk,
        pmladek@...e.com, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+d9e482e303930fa4f6ff@...kaller.appspotmail.com
Subject: Re: [PATCH] ext4: fix memory leak in ext4_fill_super

On Fri, Apr 30, 2021 at 01:05:47AM +0300, Pavel Skripkin wrote:
> > out of the thread function.  That means hanging struct mmpd_data off
> > the struct ext4_sb_info structure, and then adding a function like
> > this to fs/ext4/mmp.c
> > 
> > static void ext4_stop_mmpd(struct ext4_sb_info *sbi)

That should "extern void ...", since it will be called from
fs/ext4/super.c.  I had originally was thinking to put this function
in fs/ext4/super.c, but from the perspective of keeping the MMP code
in the same source file, it probably makes sense to keep this function
with the other MMP functions.

> > {
> > 	if (sbi->s_mmp_tsk) {
> > 		kthread_stop(sbi->s_mmp_tsk);
> > 		brelse(sbi->s_mmp_data->bh);
> > 		kfree(sbi->s_mmp_data);
> > 		sbi->s_mmp_data = NULL;
> > 		sbi->s_mmp_tsk = NULL;
> > 	}
> > }
> > 
> > Basically, just move all of the cleanup so it is done after the
> > kthread is stopped, so we don't have to do any fancy error checking.
> > We just do it unconditionally.

Cheers,

						- Ted