From: Jann Horn jannh@google.com
[ 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@google.com Signed-off-by: John Johansen john.johansen@canonical.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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; }