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Tue, 19 May 2026 14:24:03 -0700 (PDT) Received: from node ([202.47.63.86]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6831187d5f0sm6891416a12.28.2026.05.19.14.24.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2026 14:24:02 -0700 (PDT) From: Muhammad Bilal To: Pablo Neira Ayuso Cc: Florian Westphal , Phil Sutter , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Muhammad Bilal Subject: [PATCH] netfilter: nf_conntrack_irc: fix parse_dcc() off-by-one OOB read Date: Tue, 19 May 2026 17:23:28 -0400 Message-ID: <20260519212328.28290-1-meatuni001@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" parse_dcc() treats data_end as an inclusive end pointer, but its only caller passes data_limit =3D ib_ptr + datalen, which points one past the last valid byte. The newline search loop iterates while tmp <=3D data_end, so when no newline is present, *tmp is read at tmp =3D=3D data_end, one byte beyond the region filled by skb_header_pointer(). irc_buffer is kmalloc'd as MAX_SEARCH_SIZE + 1 bytes and datalen is capped at MAX_SEARCH_SIZE, so the stray read does not fault. The byte is uninitialized or stale; if it contains an ASCII digit, simple_strtoul will consume it and produce a wrong DCC IP or port in the conntrack expectation. The extra allocation byte is also a fragile guard: if the cap or allocation size changes, this becomes a real out-of-bounds read. Change the loop and its post-loop check to use strict less-than, consistent with the caller's exclusive-end convention. Update the function comment accordingly. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Muhammad Bilal --- net/netfilter/nf_conntrack_irc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/netfilter/nf_conntrack_irc.c b/net/netfilter/nf_conntrack_= irc.c index 522183b9a..9a7b8f622 100644 --- a/net/netfilter/nf_conntrack_irc.c +++ b/net/netfilter/nf_conntrack_irc.c @@ -59,7 +59,7 @@ static const char *const dccprotos[] =3D { /* tries to get the ip_addr and port out of a dcc command * return value: -1 on failure, 0 on success * data pointer to first byte of DCC command data - * data_end pointer to last byte of dcc command data + * data_end one past end of data * ip returns parsed ip of dcc command * port returns parsed port of dcc command * ad_beg_p returns pointer to first byte of addr data @@ -77,10 +77,10 @@ static int parse_dcc(char *data, const char *data_end, = __be32 *ip, =20 /* Make sure we have a newline character within the packet boundaries * because simple_strtoul parses until the first invalid character. */ - for (tmp =3D data; tmp <=3D data_end; tmp++) + for (tmp =3D data; tmp < data_end; tmp++) if (*tmp =3D=3D '\n') break; - if (tmp > data_end || *tmp !=3D '\n') + if (tmp >=3D data_end || *tmp !=3D '\n') return -1; =20 *ad_beg_p =3D data; --=20 2.54.0