From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Date: Thu, 09 Jul 2020 16:59:34 +0000 Subject: Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong() Message-Id: <20200709165934.GD9247@paulmck-ThinkPad-P72> List-Id: References: <20200709104818.GC20875@mwanda> In-Reply-To: <20200709104818.GC20875@mwanda> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dan Carpenter Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Sebastian Andrzej Siewior , Kaitao Cheng , linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote: > The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the > > >= to prevent a read one element beyond the end of the array. > > Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics") > Signed-off-by: Dan Carpenter Good eyes, thank you! Folding this into the original with attribution. Thanx, Paul > --- > kernel/smp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/smp.c b/kernel/smp.c > index 78b602cae6c2..f49966713ac3 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t > *bug_id = atomic_inc_return(&csd_bug_count); > cpu = csd_lock_wait_getcpu(csd); > smp_mb(); // No stale cur_csd values! > - if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu)) > + if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu)) > cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0)); > else > cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu)); > -- > 2.27.0 >