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SubjectRe: [perf] yet another 32/64-bit range check failure
On Wed, Apr 23, 2014 at 12:14:52AM -0400, Vince Weaver wrote:
> On Tue, 22 Apr 2014, Vince Weaver wrote:
>
> > This is allowing events to be allocated memory but not being freed somehow
> > before returning EINVAL (a memory leak).
> > At least it looks like this is happening in the huge traces I have trying
> > to track down the perf_fuzzer memory corruption bug.
>
> I can't find where the memory leak happens, but it looks like this in the
> trace:
>
> [ 3524.626452] perf_fuz-1798 0.... 1271584315us : sys_enter: NR 298 (698e40, 706, ffffffff, f, 800000000000, 800000000000)
> [ 3524.642312] perf_fuz-1798 0.... 1271584324us : kmalloc: call_site=ffffffff8113a575 ptr=ffff88007d5b0800 bytes_req=1272 bytes_alloc=2048 gfp_flags=GFP_KERNEL|GFP_ZERO
> [ 3524.662598] perf_fuz-1798 0.... 1271584337us : sys_exit: NR 298 = -22
>
> The call site for the kmalloc is in perf_event_alloc()
>
> The memory is eventually freed as:
>
> [ 3547.895534] <idle>-0 0.Ns. 1271595088us : kfree: call_site=ffffffff811316aa ptr=ffff88007d5b0800

So perf_event_open() -> err_alloc: -> free_event() -> __free_event() ->
call_rcu() -> free_event_rcu() -> kfree().

Would explain that, right? The memory is RCU freed, which means we need
to wait a grace period before releasing it.


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