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Commit 1f8266ff authored by Jann Horn's avatar Jann Horn Committed by John Johansen
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apparmor: don't try to replace stale label in ptrace access check 



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: b2d09ae4 ("apparmor: move ptrace checks to using labels")
Signed-off-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarJohn Johansen <john.johansen@canonical.com>
parent 5f997580

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;

}