[PATCH 4.19 016/131] apparmor: don't try to replace stale label in ptraceme check

Sasha Levin
2020-06-29T20:05:12Z

From: Jann Horn <jannh@google.com>

[ Upstream commit ca3fde5214e1d24f78269b337d3f22afd6bf445e ]

begin_current_label_crit_section() must run in sleepable context because
when label_is_stale() is true, aa_replace_current_label() runs, which uses
prepare_creds(), which can sleep.

Until now, the ptraceme access check (which runs with tasklist_lock held)
violated this rule.

Fixes: b2d09ae449ced ("apparmor: move ptrace checks to using labels")
Reported-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
security/apparmor/lsm.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 5e32fe434140e..898752b818dc5 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -130,11 +130,11 @@ static int apparmor_ptrace_traceme(struct task_struct *parent)
struct aa_label *tracer, *tracee;
int error;

- tracee = begin_current_label_crit_section();
+ tracee = __begin_current_label_crit_section();
tracer = aa_get_task_label(parent);
error = aa_may_ptrace(tracer, tracee, AA_PTRACE_TRACE);
aa_put_label(tracer);
- end_current_label_crit_section(tracee);
+ __end_current_label_crit_section(tracee);

return error;
}
--
2.25.1