From: John Johansen <john.johansen@canonical.com>
To: Jann Horn <jannh@google.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] apparmor: enforce nullbyte at end of tag string
Date: Tue, 28 May 2019 12:05:41 -0700 [thread overview]
Message-ID: <25ad5770-2ab3-10d0-8d51-62d7c5f9aeda@canonical.com> (raw)
In-Reply-To: <20190528153226.248785-1-jannh@google.com>
On 5/28/19 8:32 AM, Jann Horn wrote:
> A packed AppArmor policy contains null-terminated tag strings that are read
> by unpack_nameX(). However, unpack_nameX() uses string functions on them
> without ensuring that they are actually null-terminated, potentially
> leading to out-of-bounds accesses.
>
> Make sure that the tag string is null-terminated before passing it to
> strcmp().
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Jann Horn <jannh@google.com>
gah! yes!
Acked-by: John Johansen <john.johansen@canonical.com>
> ---
> Warning: The existence of this bug has not been verified at runtime, and
> the patch is compile-tested only. I noticed this while browsing through
> the code, but didn't want to spend the time necessary to figure out how
> to actually test this at runtime.
>
>
> security/apparmor/policy_unpack.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c
> index f6c2bcb2ab14..33041c4fb69f 100644
> --- a/security/apparmor/policy_unpack.c
> +++ b/security/apparmor/policy_unpack.c
> @@ -276,7 +276,7 @@ static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name)
> char *tag = NULL;
> size_t size = unpack_u16_chunk(e, &tag);
> /* if a name is specified it must match. otherwise skip tag */
> - if (name && (!size || strcmp(name, tag)))
> + if (name && (!size || tag[size-1] != '\0' || strcmp(name, tag)))
> goto fail;
> } else if (name) {
> /* if a name is specified and there is no name tag fail */
>
prev parent reply other threads:[~2019-05-28 19:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-28 15:32 [PATCH] apparmor: enforce nullbyte at end of tag string Jann Horn
2019-05-28 19:05 ` John Johansen [this message]
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