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[35.245.46.111]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-67125db3459sm3754086d50.6.2026.09.13.15.16.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 13 Sep 2026 15:16:42 -0700 (PDT) Date: Sun, 13 Sep 2026 18:16:42 -0400 From: Willem de Bruijn To: Mark Amirkan via B4 Relay , Willem de Bruijn , netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Paolo Abeni , Eric Dumazet , Simon Horman , Chetan Loke , Jakub Kicinski , "David S. Miller" Message-ID: In-Reply-To: <20260913-b4-send-packet-private-v1-1-925eab2cd388@gmail.com> References: <20260913-b4-send-packet-private-v1-1-925eab2cd388@gmail.com> Subject: Re: [PATCH net] net/packet: avoid truncating TPACKET_V3 private size Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Mark Amirkan via B4 Relay wrote: > From: Mark Amirkan > > tpacket_req3.tp_sizeof_priv is an unsigned int, and packet_set_ring() > validates the full value against the block size. init_prb_bdqc() then > stores it in the unsigned short blk_sizeof_priv field. > > Commit 2b6867c2ce76 ("net/packet: fix overflow in check for priv area > size") fixed the validation arithmetic, but an accepted value above > USHRT_MAX still narrows when it is stored. > > For a 131072-byte block, tp_sizeof_priv=65536 is valid. The narrowing > makes offset_to_first_pkt 48 instead of 65584, so packet records can be > placed in the private area that userspace asked the kernel to preserve. > > blk_sizeof_priv is internal state, so widen it to hold the validated > UAPI value. > > Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.") > Cc: stable@vger.kernel.org > Assisted-by: Symbolic > Signed-off-by: Mark Amirkan Reviewed-by: Willem de Bruijn > --- > net/packet/internal.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/packet/internal.h b/net/packet/internal.h > index b76e645cd7..f5c8cd0eed 100644 > --- a/net/packet/internal.h > +++ b/net/packet/internal.h > @@ -21,7 +21,7 @@ struct tpacket_kbdq_core { > unsigned int hdrlen; > unsigned char reset_pending_on_curr_blk; > unsigned short kactive_blk_num; > - unsigned short blk_sizeof_priv; > + unsigned int blk_sizeof_priv; This could be moved to avoid growing the struct. There is a 4B hole further down. But it's no big deal for this struct.