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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Tue, 15 Aug 2023 13:59:55 +0200
Message-ID: <CAMuHMdWNW4dHZmPjJ9WUqA40_4ZvAM2DqcLMe18jWgmu=9UeRw@mail.gmail.com>
Subject: Re: [PATCH] NFS: Fix sysfs server name memory leak
To:     Benjamin Coddington <bcodding@redhat.com>
Cc:     trond.myklebust@hammerspace.com, anna@kernel.org,
        aahringo@redhat.com, linux-nfs@vger.kernel.org,
        linux-renesas-soc@vger.kernel.org,
        Linux regressions mailing list <regressions@lists.linux.dev>
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CC regressions

On Fri, Jul 14, 2023 at 5:29 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Mon, 10 Jul 2023, Benjamin Coddington wrote:
> > Free the formatted server index string after it has been duplicated by
> > kobject_rename().
> >
> > Fixes: 1c7251187dc0 ("NFS: add superblock sysfs entries")
> > Reported-by: Alexander Aring <aahringo@redhat.com>
> > Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
>
> Thanks!
>
> This fixes the memory leaks I was seeing:
>
>      # cat /sys/kernel/debug/kmemleak
>      unreferenced object 0xc6d3b7c0 (size 64):
>        comm "mount.nfs", pid 261, jiffies 4294943450 (age 1385.530s)
>        hex dump (first 32 bytes):
>         73 65 72 76 65 72 2d 32 00 00 00 00 00 00 00 00  server-2........
>         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>        backtrace:
>         [<7849dbd6>] slab_post_alloc_hook.constprop.0+0x9c/0xac
>         [<bf2297e0>] __kmem_cache_alloc_node+0xc4/0x124
>         [<07299a52>] __kmalloc_node_track_caller+0x80/0xa4
>         [<1876b300>] kvasprintf+0x5c/0xcc
>         [<4fa40352>] kasprintf+0x28/0x58
>         [<68e29ee6>] nfs_sysfs_move_sb_to_server+0x18/0x50
>         [<6a98700b>] nfs_kill_super+0x18/0x34
>         [<d388276a>] deactivate_locked_super+0x50/0x88
>         [<3945c450>] cleanup_mnt+0x6c/0xc8
>         [<fb0ac980>] task_work_run+0x84/0xb4
>         [<d6ee2bd3>] do_work_pending+0x364/0x398
>         [<c7a0dcab>] slow_work_pending+0xc/0x20
>      unreferenced object 0xc6cdd6c0 (size 64):
>        comm "mount.nfs", pid 261, jiffies 4294943456 (age 1385.470s)
>        hex dump (first 32 bytes):
>         73 65 72 76 65 72 2d 31 00 00 00 00 00 00 00 00  server-1........
>         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>        backtrace:
>         [<7849dbd6>] slab_post_alloc_hook.constprop.0+0x9c/0xac
>         [<bf2297e0>] __kmem_cache_alloc_node+0xc4/0x124
>         [<07299a52>] __kmalloc_node_track_caller+0x80/0xa4
>         [<1876b300>] kvasprintf+0x5c/0xcc
>         [<4fa40352>] kasprintf+0x28/0x58
>         [<68e29ee6>] nfs_sysfs_move_sb_to_server+0x18/0x50
>         [<6a98700b>] nfs_kill_super+0x18/0x34
>         [<d388276a>] deactivate_locked_super+0x50/0x88
>         [<3945c450>] cleanup_mnt+0x6c/0xc8
>         [<fb0ac980>] task_work_run+0x84/0xb4
>         [<d6ee2bd3>] do_work_pending+0x364/0x398
>         [<c7a0dcab>] slow_work_pending+0xc/0x20
>
> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
>
> > --- a/fs/nfs/sysfs.c
> > +++ b/fs/nfs/sysfs.c
> > @@ -345,8 +345,10 @@ void nfs_sysfs_move_sb_to_server(struct nfs_server *server)
> >       int ret = -ENOMEM;
> >
> >       s = kasprintf(GFP_KERNEL, "server-%d", server->s_sysfs_id);
> > -     if (s)
> > +     if (s) {
> >               ret = kobject_rename(&server->kobj, s);
> > +             kfree(s);
> > +     }
> >       if (ret < 0)
> >               pr_warn("NFS: rename sysfs %s failed (%d)\n",
> >                                       server->kobj.name, ret);

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds