Re: [PATCH] lsm_audit: use get_task_comm

On 2017-08-28 17:54, Paul Moore wrote: > On Mon, Aug 28, 2017 at 9:58 AM, Geliang Tang <geliangtang(a)gmail.com&gt; wrote: > > get_task_comm() copys the task's comm under the task_lock, it's safer > > than directly using memcpy(). > > > > Signed-off-by: Geliang Tang <geliangtang(a)gmail.com&gt; > > --- > > security/lsm_audit.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/security/lsm_audit.c b/security/lsm_audit.c > > index 28d4c3a..555b1c4 100644 > > --- a/security/lsm_audit.c > > +++ b/security/lsm_audit.c > > @@ -221,7 +221,7 @@ static void dump_common_audit_data(struct audit_buffer *ab, > > BUILD_BUG_ON(sizeof(a->u) > sizeof(void *)*2); > > > > audit_log_format(ab, " pid=%d comm=", task_tgid_nr(current)); > > - audit_log_untrustedstring(ab, memcpy(comm, current->comm, sizeof(comm))); > > + audit_log_untrustedstring(ab, get_task_comm(comm, current)); > > > > switch (a->type) { > > case LSM_AUDIT_DATA_NONE: > > @@ -312,7 +312,7 @@ static void dump_common_audit_data(struct audit_buffer *ab, > > char comm[sizeof(tsk->comm)]; > > audit_log_format(ab, " opid=%d ocomm=", pid); > > audit_log_untrustedstring(ab, > > - memcpy(comm, tsk->comm, sizeof(comm))); > > + get_task_comm(comm, tsk)); > > [NOTE: adding the linux-audit mailing list to this thread] There was previously pushback about using get_task_comm() with its locking, which is why in this particular location, a memcpy was chosen instead. This was done in: 5deeb5cece3f9b30c8129786726b9d02c412c8ca rgb 2015-04-14 ("lsm: copy comm before calling audit_log to avoid race in string printing") From that commit: Using get_task_comm() to get a copy while acquiring the task_lock to prevent this and to prevent the result from being a mixture of old and new values of comm would incur potentially unacceptable overhead, considering that the value can be influenced by userspace and therefore untrusted anyways.