From: Jann Horn <jannh@xxxxxxxxxx>
[ Upstream commit 1f8266ff58840d698a1e96d2274189de1bdf7969 ]
As a comment above begin_current_label_crit_section() explains,
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 ptrace access check (which runs with a task lock held)
violated this rule.
Also add a might_sleep() assertion to begin_current_label_crit_section(),
because asserts are less likely to be ignored than comments.
Fixes: b2d09ae449ced ("apparmor: move ptrace checks to using labels")
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
security/apparmor/include/context.h | 2 ++
security/apparmor/lsm.c | 4 ++--
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/security/apparmor/include/context.h b/security/apparmor/include/context.h
index 6ae07e9aaa172..812cdec9dd3be 100644
--- a/security/apparmor/include/context.h
+++ b/security/apparmor/include/context.h
@@ -191,6 +191,8 @@ static inline struct aa_label *begin_current_label_crit_section(void)
{
struct aa_label *label = aa_current_raw_label();
+ might_sleep();
+
if (label_is_stale(label)) {
label = aa_get_newest_label(label);
if (aa_replace_current_label(label) == 0)
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 1346ee5be04f1..4f08023101f3c 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -108,12 +108,12 @@ static int apparmor_ptrace_access_check(struct task_struct *child,
struct aa_label *tracer, *tracee;
int error;
- tracer = begin_current_label_crit_section();
+ tracer = __begin_current_label_crit_section();
tracee = aa_get_task_label(child);
error = aa_may_ptrace(tracer, tracee,
mode == PTRACE_MODE_READ ? AA_PTRACE_READ : AA_PTRACE_TRACE);
aa_put_label(tracee);
- end_current_label_crit_section(tracer);
+ __end_current_label_crit_section(tracer);
return error;
}
--
2.20.1
