Messages in this thread Patch in this message | | | Date | Tue, 21 Jun 2011 04:44:31 -0700 | From | John Johansen <> | Subject | Re: [PATCH 7/7] ptrace: s/tracehook_tracer_task()/ptrace_parent()/ |
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On 06/20/2011 01:16 PM, Oleg Nesterov wrote: > On 06/17, Tejun Heo wrote: >> >> tracehook.h is on the way out. Rename tracehook_tracer_task() to >> ptrace_parent() and move it from tracehook.h to ptrace.h. > > I am a bit surpised you decided to keep this helper. Can't we simply > kill it? > > OK, we will see. I guess this change is mostly needed to remove yet > another function from tracehook.h. > >> @@ -216,7 +216,7 @@ static struct mm_struct *__check_mem_permission(struct task_struct *task) >> if (task_is_stopped_or_traced(task)) { >> int match; >> rcu_read_lock(); >> - match = (tracehook_tracer_task(task) == current); >> + match = (ptrace_parent(task) == current); >> rcu_read_unlock(); >> if (match && ptrace_may_access(task, PTRACE_MODE_ATTACH)) > > All we need > > if (task_is_traced(task) && task->parent == current) { > if (ptrace_may_access() > return mm; > } > > Of course I do not blame this patch, my only point is that this helper > only adds more confusion imho. > > > > >> @@ -67,7 +67,7 @@ static int may_change_ptraced_domain(struct task_struct *task, >> int error = 0; >> >> rcu_read_lock(); >> - tracer = tracehook_tracer_task(task); >> + tracer = ptrace_parent(task); >> if (tracer) { >> /* released below */ >> cred = get_task_cred(tracer); > > Hmm. And then this task_struct is used after we dropped rcu_read_lock(). > > John, is this correct? > nope this use is wrong. The following patch should fix this
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AppArmor: Fix reference to rcu protected pointer outside of rcu_read_lock
The pointer returned from tracehook_tracer_task() is only valid inside the rcu_read_lock. However the tracer pointer obtained is being passed to aa_may_ptrace outside of the rcu_read_lock critical section.
Mover the aa_may_ptrace test into the rcu_read_lock critical section, to fix this.
Signed-off-by: John Johansen <john.johansen@canonical.com> --- security/apparmor/domain.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c index c825c6e..78adc43 100644 --- a/security/apparmor/domain.c +++ b/security/apparmor/domain.c @@ -73,7 +73,6 @@ static int may_change_ptraced_domain(struct task_struct *task, cred = get_task_cred(tracer); tracerp = aa_cred_profile(cred); } - rcu_read_unlock(); /* not ptraced */ if (!tracer || unconfined(tracerp)) @@ -82,6 +81,7 @@ static int may_change_ptraced_domain(struct task_struct *task, error = aa_may_ptrace(tracer, tracerp, to_profile, PTRACE_MODE_ATTACH); out: + rcu_read_unlock(); if (cred) put_cred(cred); -- 1.7.4.1
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