apparmor: don't try to replace stale label in ptrace access check (1f8266ff) · Commits · 戴 / test

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: ("apparmor: move ptrace checks to using labels") Signed-off-by:

Jann Horn <jannh@google.com> Signed-off-by:

John Johansen <john.johansen@canonical.com>

security/apparmor/include/cred.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -151,6 +151,8 @@ 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)

security/apparmor/lsm.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -114,13 +114,13 @@ 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;
		}

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