lkml.org 
[lkml]   [2014]   [Jan]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.8 110/166] selinux: selinux_setprocattr()->ptrace_parent() needs rcu_read_lock()
    Date
    3.8.13.16 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Oleg Nesterov <oleg@redhat.com>

    commit c0c1439541f5305b57a83d599af32b74182933fe upstream.

    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 <emcnabb@redhat.com>
    Signed-off-by: Oleg Nesterov <oleg@redhat.com>
    Signed-off-by: Paul Moore <pmoore@redhat.com>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    security/selinux/hooks.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
    index 0963169..6b0b250 100644
    --- a/security/selinux/hooks.c
    +++ b/security/selinux/hooks.c
    @@ -5455,11 +5455,11 @@ 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,
    --
    1.8.3.2


    \
     
     \ /
      Last update: 2014-01-15 23:41    [W:3.492 / U:0.036 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site