2020-03-29 15:00:31

by Xiyu Yang

Subject: [PATCH] apparmor: fix potential label refcnt leak in aa_change_profile

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 <[email protected]>
Signed-off-by: Xin Tan <[email protected]>
---
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();

if (*fqname == '&') {
--
2.7.4

2020-04-04 23:43:24

by John Johansen

Subject: Re: [PATCH] apparmor: fix potential label refcnt leak in aa_change_profile

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 <[email protected]>
> Signed-off-by: Xin Tan <[email protected]>
> ---
> 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 == '&') {
>