From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sun, 24 Nov 2013 14:40:57 +0100 From: Borislav Petkov To: Frederic Weisbecker Cc: LKML , Oleg Nesterov , stable@vger.kernel.org Subject: Re: [PATCH 2/4] x86: Fix the hw_breakpoint range check Message-ID: <20131124134057.GA4531@pd.tnic> References: <1385289171-3411-1-git-send-email-fweisbec@gmail.com> <1385289171-3411-3-git-send-email-fweisbec@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1385289171-3411-3-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: On Sun, Nov 24, 2013 at 11:32:49AM +0100, Frederic Weisbecker wrote: > From: Oleg Nesterov > > arch_check_bp_in_kernelspace() tries to avoid the overflow and does 2 > TASK_SIZE checks but it needs OR, not AND. Consider va = TASK_SIZE -1 > and len = 2 case. > > Note: TASK_SIZE doesn't look right at least on x86, I think it should > be replaced by TASK_SIZE_MAX. > > Signed-off-by: Oleg Nesterov > Fixes: 0067f1297241ea567f2b22a455519752d70fcca9 > Cc: > Signed-off-by: Frederic Weisbecker > --- > arch/x86/kernel/hw_breakpoint.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c > index f66ff16..1131c1f 100644 > --- a/arch/x86/kernel/hw_breakpoint.c > +++ b/arch/x86/kernel/hw_breakpoint.c > @@ -200,7 +200,7 @@ int arch_check_bp_in_kernelspace(struct perf_event *bp) > va = info->address; > len = get_hbp_len(info->len); > > - return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE); > + return (va >= TASK_SIZE) || ((va + len - 1) >= TASK_SIZE); Well, can't you simplify it even further? return (va + len - 1) >= TASK_SIZE; AFAICT, the high end of the range matters, no? Unless the original code was meant to short-circuit at the first comparison already... -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --