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[35.245.46.111]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-67a7a19b1d8sm2196764d50.22.2026.10.28.11.47.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 11:47:44 -0700 (PDT) Date: Wed, 28 Oct 2026 14:47:44 -0400 From: Willem de Bruijn To: Eric Dumazet , "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Willem de Bruijn , netdev@vger.kernel.org, edumazet@kernel.org, Kyle Zeng , stable@vger.kernel.org, Willem de Bruijn Message-ID: In-Reply-To: <20261028181450.2221013-1-edumazet@kernel.org> References: <20261028181450.2221013-1-edumazet@kernel.org> Subject: Re: [PATCH net] net/packet: check TX_RING fragments before memory accounting X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Eric Dumazet wrote: > From: Kyle Zeng > > tpacket_fill_skb() adds the full non-linear payload length to > skb->truesize and sk_wmem_alloc before checking MAX_SKB_FRAGS. With > PACKET_VNET_HDR, userspace can submit a ring-sized frame even when it > greatly exceeds the device MTU. > > A near-INT_MAX frame can saturate sk_wmem_alloc before the fragment > loop rejects it. A subsequent refcount_add(0x40000001) can temporarily > turn REFCOUNT_SATURATED into 1. A concurrent TX completion can then > drop that apparent last reference and free the still-live packet > socket before refcount_warn_saturate() restores the counter. > > Check that the remaining payload fits in MAX_SKB_FRAGS pages before > accounting it. Include the initial page offset in the calculation, > and move the existing -EFAULT handling out of the fragment loop. > This preserves the accepted packet sizes and error code while > preventing an invalid frame from injecting an oversized byte charge. > > Fixes: 69e3c75f4d54 ("net: TX_RING and packet mmap") > Cc: stable@vger.kernel.org > Cc: Willem de Bruijn > Signed-off-by: Kyle Zeng > [edumazet: use net_warn_ratelimited() instead of pr_err(), add a Fixes: tag] > Signed-off-by: Eric Dumazet Reviewed-by: Willem de Bruijn