Messages in this thread | | | Subject | Re: [PATCH] apparmor: don't try to replace stale label in ptrace access check | From | John Johansen <> | Date | Thu, 13 Sep 2018 09:23:12 -0700 |
| |
On 09/13/2018 09:12 AM, Jann Horn wrote: > 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>
oh ouch, thanks Jann nice catch. I've pulled it into apparmor-next
Acked-by: John Johansen <john.johansen@canonical.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; > } >
| |