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Thu, 16 Apr 2026 03:09:49 -0700 (PDT) Received: from [192.168.88.32] ([150.228.93.122]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488f5813665sm43475935e9.2.2026.04.16.03.09.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Apr 2026 03:09:49 -0700 (PDT) Message-ID: Date: Thu, 16 Apr 2026 12:09:47 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] net: dsa: sja1105: fix division by zero in sja1105_tas_set_runtime_params() To: Alexander.Chesnokov@kaspersky.com, olteanv@gmail.com Cc: lvc-project@linuxtesting.org, Oleg.Kazakov@kaspersky.com, Pavel.Zhigulin@kaspersky.com, stable@vger.kernel.org, Andrew Lunn , Florian Fainelli , "David S. Miller" , Eric Dumazet , Jakub Kicinski , linux-kernel@vger.kernel.org, netdev@vger.kernel.org References: <20260413085140.33138-1-Alexander.Chesnokov@kaspersky.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20260413085140.33138-1-Alexander.Chesnokov@kaspersky.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/13/26 10:51 AM, Alexander.Chesnokov@kaspersky.com wrote: > From: Alexander Chesnokov > > If taprio offload is configured such that none of the ports' base_time > is less than S64_MAX (the initial value of earliest_base_time), then > its_cycle_time remains zero and is passed to future_base_time() as > cycle_time, causing division by zero in div_s64(). > > Add a check for its_cycle_time being zero before calling > future_base_time() and return -EINVAL. > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > Fixes: 86db36a347b4 ("net: dsa: sja1105: Implement state machine for TAS with PTP clock source") > Cc: stable@vger.kernel.org > No empty lines in the tag area. > Signed-off-by: Alexander Chesnokov > --- > drivers/net/dsa/sja1105/sja1105_tas.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/net/dsa/sja1105/sja1105_tas.c b/drivers/net/dsa/sja1105/sja1105_tas.c > index e6153848a950..ce4b544a2b9c 100644 > --- a/drivers/net/dsa/sja1105/sja1105_tas.c > +++ b/drivers/net/dsa/sja1105/sja1105_tas.c > @@ -62,6 +62,9 @@ static int sja1105_tas_set_runtime_params(struct sja1105_private *priv) > if (!tas_data->enabled) > return 0; > > + if (!its_cycle_time) > + return -EINVAL; Sashiko says: Is this division by zero reachable without this check? When all ports have base_time == S64_MAX, earliest_base_time and latest_base_time are both S64_MAX. When future_base_time(S64_MAX, 0, S64_MAX) is called, it returns early because base_time >= now (S64_MAX >= S64_MAX), avoiding the division. Could this new error path cause an actual division by zero later? When returning -EINVAL here, tas_data->enabled is already set to true, but tas_data->max_cycle_time is left uninitialized (0). If sja1105_tas_state_machine() runs later, it will pass this max_cycle_time as the cycle_time argument to future_base_time(). Since 0 >= now + 1s is false, it proceeds to call div_s64() with a zero divisor. /P