Re: [PATCH v2 1/2] auditsc: audit_krule mask accesses need bounds checking

On Wed, 2014-05-28 at 19:27 -0700, Andy Lutomirski wrote: > On Wed, May 28, 2014 at 7:23 PM, Eric Paris <eparis(a)redhat.com&gt; wrote: > > On Wed, 2014-05-28 at 18:44 -0700, Andy Lutomirski wrote: > >> Fixes an easy DoS and possible information disclosure. > >> > >> This does nothing about the broken state of x32 auditing. > >> > >> Cc: stable(a)vger.kernel.org > >> Signed-off-by: Andy Lutomirski <luto(a)amacapital.net&gt; > >> --- > >> > >> kernel/auditsc.c | 27 ++++++++++++++++++--------- > >> 1 file changed, 18 insertions(+), 9 deletions(-) > >> > >> diff --git a/kernel/auditsc.c b/kernel/auditsc.c > >> index f251a5e..7ccd9db 100644 > >> --- a/kernel/auditsc.c > >> +++ b/kernel/auditsc.c > >> @@ -728,6 +728,22 @@ static enum audit_state audit_filter_task(struct > >> task_struct *tsk, char **key)> >> > >> return AUDIT_BUILD_CONTEXT; > >> } > >> > >> +static bool audit_in_mask(const struct audit_krule *rule, unsigned > >> long val) +{ > >> + int word, bit; > >> + > >> + if (val > 0xffffffff) > >> + return false; > > > > Why is this necessary? > > To avoid an integer overflow. Admittedly, this particular overflow > won't cause a crash, but it will cause incorrect results.

You know this code pre-dates git? I admit, I'm shocked no one ever noticed it before! This is ANCIENT. And clearly broken. I'll likely ask Richard to add a WARN_ONCE() in both this place, and below in word > AUDIT_BITMASK_SIZE so we might know if we ever need a larger bitmask to store syscall numbers....