From: John Johansen <john.johansen@canonical.com>
To: Xiyu Yang <xiyuyang19@fudan.edu.cn>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: yuanxzhang@fudan.edu.cn, kjlu@umn.edu, Xin Tan <tanxin.ctf@gmail.com>
Subject: Re: [PATCH] apparmor: fix potential label refcnt leak in aa_change_profile
Date: Sat, 4 Apr 2020 16:35:16 -0700 [thread overview]
Message-ID: <2d905eaf-749f-e2c5-f1fa-51806848e50f@canonical.com> (raw)
In-Reply-To: <1585493861-9867-1-git-send-email-xiyuyang19@fudan.edu.cn>
On 3/29/20 7:57 AM, Xiyu Yang wrote:
> aa_change_profile() invokes aa_get_current_label(), which returns
> a reference of the current task's label.
>
> According to the comment of aa_get_current_label(), the returned
> reference must be put with aa_put_label().
> However, when the original object pointed by "label" becomes
> unreachable because aa_change_profile() returns or a new object
> is assigned to "label", reference count increased by
> aa_get_current_label() is not decreased, causing a refcnt leak.
>
> Fix this by calling aa_put_label() before the original object pointed
> by "label" becomes unreachable.
>
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
> ---
> security/apparmor/domain.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
> index 6ceb74e0f789..b99145ae34c0 100644
> --- a/security/apparmor/domain.c
> +++ b/security/apparmor/domain.c
> @@ -1328,6 +1328,7 @@ int aa_change_profile(const char *fqname, int flags)
> ctx->nnp = aa_get_label(label);
>
> if (!fqname || !*fqname) {
> + aa_put_label(label);
> AA_DEBUG("no profile name");
> return -EINVAL;
> }
> @@ -1346,6 +1347,7 @@ int aa_change_profile(const char *fqname, int flags)
> op = OP_CHANGE_PROFILE;
> }
>
> + aa_put_label(label);
> label = aa_get_current_label();
this isn't quite right. Instead of adding the put_label here,
the aa_get_current_label needs to be dropped, as it isn't needed because
it gets called earlier in the fn.
can you refresh with this change
>
> if (*fqname == '&') {
>
prev parent reply other threads:[~2020-04-04 23:35 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-29 14:57 [PATCH] apparmor: fix potential label refcnt leak in aa_change_profile Xiyu Yang
2020-04-04 23:35 ` John Johansen [this message]
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