From: Jann Horn Date: Thu, 13 Sep 2018 16:12:09 +0000 (+0200) Subject: apparmor: don't try to replace stale label in ptrace access check X-Git-Tag: rel_imx_5.10.35_2.0.0-somdevices.0~5980^2~9 X-Git-Url: https://git.somdevices.com/?a=commitdiff_plain;h=1f8266ff58840d698a1e96d2274189de1bdf7969;p=linux.git 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: b2d09ae449ced ("apparmor: move ptrace checks to using labels") Signed-off-by: Jann Horn Signed-off-by: John Johansen --- diff --git a/security/apparmor/include/cred.h b/security/apparmor/include/cred.h index e287b7d0d4be..265ae6641a06 100644 --- a/security/apparmor/include/cred.h +++ b/security/apparmor/include/cred.h @@ -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) diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c index 74f17376202b..f09fea0b4db7 100644 --- a/security/apparmor/lsm.c +++ b/security/apparmor/lsm.c @@ -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; }