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apparmor: Fix aa_label refcnt leak in policy_update

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commit c6b39f070722ea9963ffe756bfe94e89218c5e63 upstream.

policy_update() invokes begin_current_label_crit_section(), which
returns a reference of the updated aa_label object to "label" with
increased refcount.

When policy_update() returns, "label" becomes invalid, so the refcount
should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
policy_update(). When aa_may_manage_policy() returns not NULL, the
refcnt increased by begin_current_label_crit_section() is not decreased,
causing a refcnt leak.

Fix this issue by jumping to "end_section" label when
aa_may_manage_policy() returns not NULL.

Fixes: 5ac8c355ae ("apparmor: allow introspecting the loaded policy pre internal transform")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Xiyu Yang 2020-04-20 13:35:28 +08:00 committed by Greg Kroah-Hartman
parent dd73adb161
commit c701849502
1 changed files with 2 additions and 1 deletions
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3
security/apparmor/apparmorfs.c
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@ -424,7 +424,7 @@ static ssize_t policy_update(u32 mask, const char __user *buf, size_t size,
*/
error = aa_may_manage_policy(label, ns, mask);
if (error)
return error;
goto end_section;
data = aa_simple_write_to_buffer(buf, size, size, pos);
error = PTR_ERR(data);
@ -432,6 +432,7 @@ static ssize_t policy_update(u32 mask, const char __user *buf, size_t size,
error = aa_replace_profiles(ns, label, mask, data);
aa_put_loaddata(data);
}
end_section:
end_current_label_crit_section(label);
return error;