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[76.102.12.149]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-354894acb47sm174006a91.10.2026.02.03.18.03.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Feb 2026 18:03:38 -0800 (PST) Date: Tue, 3 Feb 2026 18:03:37 -0800 From: Stanislav Fomichev To: "Rao, Nikhil" Cc: magnus.karlsson@intel.com, maciej.fijalkowski@intel.com, sdf@fomichev.me, netdev@vger.kernel.org Subject: Re: net/xdp: Potential issue with xp_aligned_validate_desc() in multi-buffer packets Message-ID: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On 02/03, Rao, Nikhil wrote: > Hi XDP maintainers, > > I have noticed a potential issue with multi-buffer packet support in the > xp_aligned_validate_desc() function in net/xdp/xsk_queue.h. > > In xp_aligned_validate_desc(), the validation always adjusts the address > and length by pool->tx_metadata_len: > >   u64 addr = desc->addr - pool->tx_metadata_len; >   u64 len = desc->len + pool->tx_metadata_len; > > However, in multi-buffer XDP packets, only the first descriptor contains > TX metadata. Subsequent descriptors do not have > metadata and should not be validated with this adjustment. > > This causes validation failures for the 2nd buffer onward in > multi-buffer packets when TX metadata is enabled. > > The same issue exists in xp_unaligned_validate_desc() as well. > > I'm happy to submit a patch if this is indeed a bug. Please let me know > your thoughts. I think your assessment is correct. Can you try to extend prog_tests/xdp_metadata.c to send a mbuf packet? I don't think we have any real test coverage for the metadata+mbuf..