From: Oleg Nesterov Date: Mon, 23 Dec 2013 22:45:01 +0000 (-0500) Subject: selinux: selinux_setprocattr()->ptrace_parent() needs rcu_read_lock() X-Git-Tag: firefly_0821_release~176^2~4724^2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c0c1439541f5305b57a83d599af32b74182933fe;p=firefly-linux-kernel-4.4.55.git selinux: selinux_setprocattr()->ptrace_parent() needs rcu_read_lock() selinux_setprocattr() does ptrace_parent(p) under task_lock(p), but task_struct->alloc_lock doesn't pin ->parent or ->ptrace, this looks confusing and triggers the "suspicious RCU usage" warning because ptrace_parent() does rcu_dereference_check(). And in theory this is wrong, spin_lock()->preempt_disable() doesn't necessarily imply rcu_read_lock() we need to access the ->parent. Reported-by: Evan McNabb Signed-off-by: Oleg Nesterov Cc: stable@vger.kernel.org Signed-off-by: Paul Moore --- diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 5db26468b5c3..6625699f497c 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -5588,11 +5588,11 @@ static int selinux_setprocattr(struct task_struct *p, /* Check for ptracing, and update the task SID if ok. Otherwise, leave SID unchanged and fail. */ ptsid = 0; - task_lock(p); + rcu_read_lock(); tracer = ptrace_parent(p); if (tracer) ptsid = task_sid(tracer); - task_unlock(p); + rcu_read_unlock(); if (tracer) { error = avc_has_perm(ptsid, sid, SECCLASS_PROCESS,