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Fri, 17 Apr 2026 18:34:54 +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 qd3zDE594mmFFQAAD6G6ig (envelope-from ); Fri, 17 Apr 2026 18:34:54 +0000 From: Fernando Fernandez Mancera To: netfilter-devel@vger.kernel.org Cc: netdev@vger.kernel.org, coreteam@netfilter.org, pablo@netfilter.org, fw@strlen.de, phil@nwl.cc, Fernando Fernandez Mancera Subject: [PATCH 1/4 nf] netfilter: nft_exthdr: skip SCTP chunk evaluation for non-first fragments Date: Fri, 17 Apr 2026 20:34:30 +0200 Message-ID: <20260417183433.4739-1-fmancera@suse.de> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[99.99%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; FUZZY_RATELIMITED(0.00)[rspamd.com]; URIBL_BLOCKED(0.00)[suse.de:mid,suse.de:dkim,suse.de:email,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCPT_COUNT_SEVEN(0.00)[7]; FROM_EQ_ENVFROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.de:dkim,suse.de:email,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns] X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -3.01 X-Spam-Level: X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Queue-Id: AC1836A9E8 The SCTP chunk matching logic in nft_exthdr relies on SCTP common header being present at the transport header offset. For fragmented packets at IP level, only the first fragment would match this condition. The nft_exthdr could be used in a PREROUTING chain with a priority lower than -400. This would bypass defragmentation. In addition, it can be use in stateless environments so it should work on a environment where defragmentation is not being performed at all. Add a check for pkt->fragoff to ensure exthdr SCTP only evaluates unfragmented packets or the first fragment in the stream. Fixes: 133dc203d77d ("netfilter: nft_exthdr: Support SCTP chunks") Signed-off-by: Fernando Fernandez Mancera --- net/netfilter/nft_exthdr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c index 7eedf4e3ae9c..8eb708bb8cff 100644 --- a/net/netfilter/nft_exthdr.c +++ b/net/netfilter/nft_exthdr.c @@ -376,7 +376,7 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr, const struct sctp_chunkhdr *sch; struct sctp_chunkhdr _sch; - if (pkt->tprot != IPPROTO_SCTP) + if (pkt->tprot != IPPROTO_SCTP || pkt->fragoff) goto err; do { -- 2.53.0