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authorJann Horn <jannh@google.com>2018-09-13 19:12:09 +0300
committerJohn Johansen <john.johansen@canonical.com>2018-09-13 19:44:56 +0300
commit1f8266ff58840d698a1e96d2274189de1bdf7969 (patch)
tree22ec503efa895edcbc8a0bdd465d4206cad19311
parent5f997580e8b12b9f585e34cc16304925d26ce49e (diff)
downloadlinux-1f8266ff58840d698a1e96d2274189de1bdf7969.tar.xz
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 <jannh@google.com> Signed-off-by: John Johansen <john.johansen@canonical.com>
-rw-r--r--security/apparmor/include/cred.h2
-rw-r--r--security/apparmor/lsm.c4
2 files changed, 4 insertions, 2 deletions
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;
}