From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
To: Eric Biggers <ebiggers@kernel.org>
Cc: linux-crypto@vger.kernel.org,
Herbert Xu <herbert@gondor.apana.org.au>,
syzkaller-bugs@googlegroups.com, linux-hardening@vger.kernel.org,
linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
Jann Horn <jannh@google.com>, Kees Cook <keescook@chromium.org>,
Elena Petrova <lenaptr@google.com>,
Vegard Nossum <vegard.nossum@oracle.com>,
stable@vger.kernel.org,
syzbot+92ead4eb8e26a26d465e@syzkaller.appspotmail.com
Subject: Re: [PATCH] crypto: af_alg - avoid undefined behavior accessing salg_name
Date: Mon, 26 Oct 2020 18:10:59 -0500 [thread overview]
Message-ID: <20201026231059.GB26823@embeddedor> (raw)
In-Reply-To: <20201026212148.GA26823@embeddedor>
On Mon, Oct 26, 2020 at 04:21:48PM -0500, Gustavo A. R. Silva wrote:
> > +/*
> > + * Linux v4.12 and later removed the 64-byte limit on salg_name[]; it's now an
> > + * arbitrary-length field. We had to keep the original struct above for source
> > + * compatibility with existing userspace programs, though. Use the new struct
> > + * below if support for very long algorithm names is needed. To do this,
> > + * allocate 'sizeof(struct sockaddr_alg_new) + strlen(algname) + 1' bytes, and
> > + * copy algname (including the null terminator) into salg_name.
> > + */
> > +struct sockaddr_alg_new {
> > + __u16 salg_family;
> > + __u8 salg_type[14];
> > + __u32 salg_feat;
> > + __u32 salg_mask;
> > + __u8 salg_name[];
> > +};
> > +
>
> How something like this, instead:
>
> struct sockaddr_alg {
> - __u16 salg_family;
> - __u8 salg_type[14];
> - __u32 salg_feat;
> - __u32 salg_mask;
> - __u8 salg_name[64];
> + union {
> + struct {
> + __u16 salg_v1_family;
> + __u8 salg_v1_type[14];
> + __u32 salg_v1_feat;
> + __u32 salg_v1_mask;
> + __u8 salg_name[64];
> + };
> + struct {
> + __u16 salg_family;
> + __u8 salg_type[14];
> + __u32 salg_feat;
> + __u32 salg_mask;
> + __u8 salg_name_new[];
> + };
> + };
> };
>
Something similar to the following approach might work:
https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?h=testing/uapi/gntalloc&id=db46c8aba41c436edb0b4ef2941bd7390b0e5d61
--
Gustavo
next prev parent reply other threads:[~2020-10-26 23:05 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-16 8:12 UBSAN: array-index-out-of-bounds in alg_bind syzbot
2020-10-17 3:49 ` Kees Cook
2020-10-17 6:20 ` Jann Horn
2020-10-17 10:50 ` Dmitry Vyukov
2020-10-17 11:02 ` Jann Horn
2020-10-17 14:41 ` Dmitry Vyukov
2020-10-26 20:07 ` [PATCH] crypto: af_alg - avoid undefined behavior accessing salg_name Eric Biggers
2020-10-26 21:21 ` Gustavo A. R. Silva
2020-10-26 23:10 ` Gustavo A. R. Silva [this message]
2020-10-26 23:40 ` Eric Biggers
2020-10-26 21:23 ` Jann Horn
2020-10-26 21:56 ` Eric Biggers
2020-10-26 22:40 ` Jann Horn
2020-11-06 7:01 ` Herbert Xu
2020-11-02 2:17 ` UBSAN: array-index-out-of-bounds in alg_bind syzbot
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