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SubjectRE: [PATCH] net: tls: fix a memory leak bug
Date


> -----Original Message-----
> From: Jakub Kicinski <jakub.kicinski@netronome.com>
> Sent: Thursday, April 25, 2019 6:39 AM
> To: Wenwen Wang <wang6495@umn.edu>
> Cc: Boris Pismenny <borisp@mellanox.com>; Aviad Yehezkel
> <aviadye@mellanox.com>; Dave Watson <davejwatson@fb.com>; John
> Fastabend <john.fastabend@gmail.com>; Daniel Borkmann
> <daniel@iogearbox.net>; David S. Miller <davem@davemloft.net>; open
> list:NETWORKING [TLS] <netdev@vger.kernel.org>; open list <linux-
> kernel@vger.kernel.org>; Vakul Garg <vakul.garg@nxp.com>
> Subject: Re: [PATCH] net: tls: fix a memory leak bug
>
> On Wed, 24 Apr 2019 15:18:07 -0500, Wenwen Wang wrote:
> > In decrypt_internal(), a memory block 'mem' is allocated through
> > kmalloc() to hold aead_req, sgin[], sgout[], aad, and iv. This memory
> > block should be freed after it is used, before this function is
> > returned. However, if the return value of the function invocation of
> > tls_do_decryption() is -EINPROGRESS, this memory block is actually not
> > freed, which is a memory leak bug.
> >
> > To fix this issue, free the allocated block before the error code
> > -EINPROGRESS is returned.
> >
> > Signed-off-by: Wenwen Wang <wang6495@umn.edu>
>
> Did you find this by code inspection or is this provable at runtime (kmemleak
> or such)?
>
> > diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index
> > b50ced8..22445bb 100644
> > --- a/net/tls/tls_sw.c
> > +++ b/net/tls/tls_sw.c
> > @@ -1445,8 +1445,10 @@ static int decrypt_internal(struct sock *sk,
> struct sk_buff *skb,
> > /* Prepare and submit AEAD request */
> > err = tls_do_decryption(sk, skb, sgin, sgout, iv,
> > data_len, aead_req, async);
> > - if (err == -EINPROGRESS)
> > + if (err == -EINPROGRESS) {
> > + kfree(mem);
> > return err;
>
> Mm... don't think so.
>
> -EINPROGRESS is special, it means something is working on the request
> asynchronously here.
>
> I think this memory is freed in tls_decrypt_done():
>
> kfree(aead_req);
>
> Note that aead_req is the first member of the allocated buffer.
>
> CCing Vakul

The patch is wrong.
Valid reasons have been given against the patch.

>
> > + }
> >
> > /* Release the pages in case iov was mapped to pages */
> > for (; pages > 0; pages--)

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