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Wed, 1 Apr 2026 23:53:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id zwtDFPOvzWmvMgAAD6G6ig (envelope-from ); Wed, 01 Apr 2026 23:53:23 +0000 Message-ID: <4cce92eb-61a0-4869-8a30-b86d65e8a675@suse.de> Date: Thu, 2 Apr 2026 01:53:14 +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-next v4 1/2] net: hsr: require valid EOT supervision TLV To: Luka Gejak , davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: netdev@vger.kernel.org, fmaurer@redhat.com, horms@kernel.org References: <20260401092324.52266-1-luka.gejak@linux.dev> <20260401092324.52266-2-luka.gejak@linux.dev> <2d94a1a6-e6c5-427c-b10f-63377cb10407@suse.de> Content-Language: en-US From: Fernando Fernandez Mancera In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.30 X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCPT_COUNT_SEVEN(0.00)[8]; MID_RHS_MATCH_FROM(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[linux.dev:email,imap1.dmz-prg2.suse.org:helo,suse.de:mid] X-Spam-Flag: NO On 4/1/26 6:59 PM, Luka Gejak wrote: > On Wed Apr 1, 2026 at 4:47 PM CEST, Fernando Fernandez Mancera wrote: >> On 4/1/26 11:23 AM, luka.gejak@linux.dev wrote: >>> From: Luka Gejak >>> >>> Supervision frames are only valid if terminated with a zero-length EOT >>> TLV. The current check fails to reject non-EOT entries as the terminal >>> TLV, potentially allowing malformed supervision traffic. >>> >>> Fix this by strictly requiring the terminal TLV to be HSR_TLV_EOT >>> with a length of zero. >>> >>> Reviewed-by: Felix Maurer >>> Signed-off-by: Luka Gejak >>> --- >>> net/hsr/hsr_forward.c | 41 ++++++++++++++++++++++------------------- >>> 1 file changed, 22 insertions(+), 19 deletions(-) >>> >>> diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c >>> index 0aca859c88cb..17b705235c4a 100644 >>> --- a/net/hsr/hsr_forward.c >>> +++ b/net/hsr/hsr_forward.c >>> @@ -82,39 +82,42 @@ static bool is_supervision_frame(struct hsr_priv *hsr, struct sk_buff *skb) >>> hsr_sup_tag->tlv.HSR_TLV_length != sizeof(struct hsr_sup_payload)) >>> return false; >>> >>> - /* Get next tlv */ >>> + /* Advance past the first TLV payload to reach next TLV header */ >>> total_length += hsr_sup_tag->tlv.HSR_TLV_length; >>> - if (!pskb_may_pull(skb, total_length)) >>> + /* Linearize next TLV header before access */ >>> + if (!pskb_may_pull(skb, total_length + sizeof(struct hsr_sup_tlv))) >>> return false; >>> skb_pull(skb, total_length); >>> hsr_sup_tlv = (struct hsr_sup_tlv *)skb->data; >>> skb_push(skb, total_length); >>> >>> - /* if this is a redbox supervision frame we need to verify >>> - * that more data is available >>> + /* Walk through TLVs to find end-of-TLV marker, skipping any unknown >>> + * extension TLVs to maintain forward compatibility. >>> */ >>> - if (hsr_sup_tlv->HSR_TLV_type == PRP_TLV_REDBOX_MAC) { >>> - /* tlv length must be a length of a mac address */ >>> - if (hsr_sup_tlv->HSR_TLV_length != sizeof(struct hsr_sup_payload)) >>> - return false; >>> + for (;;) { >>> + if (hsr_sup_tlv->HSR_TLV_type == HSR_TLV_EOT && >>> + hsr_sup_tlv->HSR_TLV_length == 0) >>> + return true; >>> >> >> I do not follow this approach, why a loop? From IEC 62439-3, I do not >> understand that supervision frames could have multiple >> PRP_TLV_REDBOX_MAC TLVs. The current code handles the TLVs correctly. >> >> Which makes me wonder, how are you testing this? Do you have some >> hardware with HSR/PRP support that is sending these frames? If so, which >> one? Are you testing this using a HSR/PRP environment with purely Linux >> devices? >> >> Thanks, >> Fernando. >> >>> - /* make sure another tlv follows */ >>> - total_length += sizeof(struct hsr_sup_tlv) + hsr_sup_tlv->HSR_TLV_length; >>> - if (!pskb_may_pull(skb, total_length)) >>> + /* Validate known TLV types */ >>> + if (hsr_sup_tlv->HSR_TLV_type == PRP_TLV_REDBOX_MAC) { >>> + if (hsr_sup_tlv->HSR_TLV_length != >>> + sizeof(struct hsr_sup_payload)) >>> + return false; >>> + } >>> + >>> + /* Advance past current TLV: header + payload */ >>> + total_length += sizeof(struct hsr_sup_tlv) + >>> + hsr_sup_tlv->HSR_TLV_length; >>> + /* Linearize next TLV header before access */ >>> + if (!pskb_may_pull(skb, >>> + total_length + sizeof(struct hsr_sup_tlv))) >>> return false; >>> >>> - /* get next tlv */ >>> skb_pull(skb, total_length); >>> hsr_sup_tlv = (struct hsr_sup_tlv *)skb->data; >>> skb_push(skb, total_length); >>> } > > Hi Fernando, > > You are right that IEC 62439-3 does not specify multiple > PRP_TLV_REDBOX_MAC TLVs. My intention with the loop was not to handle > multiple RedBox MACs, but rather to make the parser robust against > unknown TLV types. If a future revision of the standard or a vendor > extension introduces a new TLV, the loop allows the kernel to safely > skip over unrecognized TLVs by reading their length, ensuring it can > still validate the HSR_TLV_EOT marker at the end. > AFAIU, the TLVs must be in the right order. I don't know, it doesn't sound very convincing to me that we are anticipating to new TLVs. HSR/PRP isn't a very active protocol and it has few users in Kernel probably compare to other protocols because it is used in a very specific industry domain. If a new revision of the protocol specs is released we can always update our implementation. Anyway, since Felix reviewed the initial patch let's wait for his review. > However, if the preference for the HSR subsystem is strict adherence to > only currently defined TLVs over forward compatibility, I completely > understand. > > Furthermore, I am testing this using a purely Linux environment by > using a virtual HSR environment on Arch Linux. I set up two network > namespaces connected via veth pairs and instantiated HSR interfaces. > > The nodes successfully synchronized and maintained the connection. I > confirmed this by observing the expected duplicate packets (DUP!) > during ping tests between namespaces and by verifying that supervision > frames were correctly parsed, allowing the nodes to populate their > remote node tables. > > Let me know if you'd prefer I drop the loop for v5. > Best regards, > Luka Gejak >