lkml.org 
[lkml]   [2018]   [Sep]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
Subject[PATCH] apparmor: don't try to replace stale label in ptrace access check
From
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.

Signed-off-by: Jann Horn <jannh@google.com>
---
I have tested that just the might_sleep() yells a lot, and adding the
rest of the patch stops the yelling.

security/apparmor/include/cred.h | 2 ++
security/apparmor/lsm.c | 4 ++--
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 8b8b70620bbe..e3f40c20b9b4 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;
}
--
2.19.0.rc2.392.g5ba43deb5a-goog
\
 
 \ /
  Last update: 2018-09-13 18:12    [W:0.098 / U:1.628 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site