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Fri, 24 Jul 2026 09:02:25 -0700 (PDT) Date: Fri, 24 Jul 2026 09:02:21 -0700 From: Stanislav Fomichev To: Alexander Lobakin Cc: "Cen Zhang (Microsoft)" , magnus.karlsson@intel.com, maciej.fijalkowski@intel.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, sdf@fomichev.me, horms@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, AutonomousCodeSecurity@microsoft.com, tgopinath@linux.microsoft.com, kys@microsoft.com Subject: Re: [PATCH net v2] xsk: reject undersized tx_metadata at runtime validation Message-ID: References: <20260722041326.75199-1-blbllhy@gmail.com> <27dd39a0-71bd-4cff-8e72-6aa45df57dff@intel.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <27dd39a0-71bd-4cff-8e72-6aa45df57dff@intel.com> On 07/24, Alexander Lobakin wrote: > From: Stanislav Fomichev > Date: Thu, 23 Jul 2026 10:15:15 -0700 > > > On 07/23, Alexander Lobakin wrote: > >> From: Stanislav Fomichev > >> Date: Wed, 22 Jul 2026 10:55:17 -0700 > >> > >>> On 07/22, Cen Zhang (Microsoft) wrote: > >>>> There is no metadata length check before accessing struct xsk_tx_metadata > >>>> fields in both xdp_umem_reg() (registration) and > >>>> xsk_buff_valid_tx_metadata() (runtime). Thus, an invalid small > >>>> tx_metadata_len (e.g. 8 bytes) passes registration and later causes an > >>>> out-of-bounds read when xsk_skb_metadata() accesses fields beyond the > >>>> declared metadata region. > >> > >> [...] > >> > >>> @@ -773,7 +773,7 @@ struct xdp_desc_ctx xp_raw_get_ctx(const struct xsk_buff_pool *pool, u64 addr) > >>> addr = __xp_raw_get_addr(pool, addr); > >>> > >>> ret.dma = __xp_raw_get_dma(pool, addr); > >>> - ret.meta = __xsk_buff_get_metadata(pool, __xp_raw_get_data(pool, addr)); > >>> + xsk_buff_read_metadata(pool, addr, &ret.meta); > >> > >> That effectively disables some micro-optimizations that were the reason > >> I created this helper -- __xp_raw_get_data() is inline, while > >> xsk_buff_read_metadata() uses the external version, probably some other > >> stuff (note the underscored __xsk_buff_get_metadata()) =\ This function > >> expanded to have no external calls on clang -O2, with this patch I'm not > >> sure it would. > > > > Any better ideas on how to solve it? I can convert all non libeth stuff > > to these new xsk_buff_read_metadata helpers and keep xp_raw_get_ctx > > to you? Will that work? > > Sure, I can take a look. > > Do you want me to pick this patch as a base or you'd like to send a new rev? I have an idea on how to keep the existing pointer (instead of introducing a copy). Let me play with it today, will send something hopefully Monday..