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From: Ard Biesheuvel <ardb@kernel.org>
To: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: linux-efi <linux-efi@vger.kernel.org>,
	Jeremy Kerr <jk@ozlabs.org>, Matthew Garrett <mjg59@google.com>,
	David Laight <David.Laight@aculab.com>,
	Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
Subject: Re: [PATCH] efivarfs: revert "fix memory leak in efivarfs_create()"
Date: Wed, 25 Nov 2020 11:28:39 +0100
Message-ID: <CAMj1kXHHW2MSUb1emSnDPqffBVFinAO2=w5Si3toEvqXZUBY2Q@mail.gmail.com> (raw)
In-Reply-To: <309bd3399d042ca94e5bab35980d661c@natalenko.name>

On Wed, 25 Nov 2020 at 11:27, Oleksandr Natalenko
<oleksandr@natalenko.name> wrote:
>
> On 25.11.2020 08:53, Ard Biesheuvel wrote:
> > The memory leak addressed by commit fe5186cf12e3 is a false positive:
> > all allocations are recorded in a linked list, and freed when the
> > filesystem is unmounted. This leads to double frees, and as reported
> > by David, leads to crashes if SLUB is configured to self destruct when
> > double frees occur.
> >
> > So drop the redundant kfree() again, and instead, mark the offending
> > pointer variable so the allocation is ignored by kmemleak.
> >
> > Cc: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
> > Fixes: fe5186cf12e3 ("efivarfs: fix memory leak in efivarfs_create()")
> > Reported-by: David Laight <David.Laight@aculab.com>
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >  fs/efivarfs/inode.c | 1 +
> >  fs/efivarfs/super.c | 1 -
> >  2 files changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c
> > index 96c0c86f3fff..38324427a2b3 100644
> > --- a/fs/efivarfs/inode.c
> > +++ b/fs/efivarfs/inode.c
> > @@ -103,6 +103,7 @@ static int efivarfs_create(struct inode *dir,
> > struct dentry *dentry,
> >       var->var.VariableName[i] = '\0';
> >
> >       inode->i_private = var;
> > +     kmemleak_ignore(var);
>
> Do we need to do this as well:
>
> #include <linux/kmemleak.h>
>
> ?
>
> Because otherwise for 5.9 I get:
>
> [  148s] fs/efivarfs/inode.c: In function 'efivarfs_create':
> [  148s] fs/efivarfs/inode.c:106:2: error: implicit declaration of
> function 'kmemleak_ignore' [-Werror=implicit-function-declaration]
> [  148s]   106 |  kmemleak_ignore(var);
> [  148s]       |  ^~~~~~~~~~~~~~~
>

Ah yes, thanks for the report. I will add the include to the patch.


> >
> >       err = efivar_entry_add(var, &efivarfs_list);
> >       if (err)
> > diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
> > index f943fd0b0699..15880a68faad 100644
> > --- a/fs/efivarfs/super.c
> > +++ b/fs/efivarfs/super.c
> > @@ -21,7 +21,6 @@ LIST_HEAD(efivarfs_list);
> >  static void efivarfs_evict_inode(struct inode *inode)
> >  {
> >       clear_inode(inode);
> > -     kfree(inode->i_private);
> >  }
> >
> >  static const struct super_operations efivarfs_ops = {
>
> --
>    Oleksandr Natalenko (post-factum)

  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-25  7:53 Ard Biesheuvel
2020-11-25  8:05 ` Oleksandr Natalenko
2020-11-25  8:05   ` Ard Biesheuvel
2020-11-25  8:25     ` Greg Kroah-Hartman
2020-11-25 10:27 ` Oleksandr Natalenko
2020-11-25 10:28   ` Ard Biesheuvel [this message]
2020-11-27 16:50     ` Jonathon Fernyhough
2020-11-27 16:58       ` Ard Biesheuvel
2020-11-27 16:59       ` Oleksandr Natalenko

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