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Tue, 03 Nov 2026 11:33:22 -0800 (PST) Received: from localhost ([2a03:2880:9ff:6f::]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36ca38a6160sm238153eec.9.2026.11.03.11.33.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Nov 2026 11:33:21 -0800 (PST) Date: Tue, 3 Nov 2026 11:32:10 -0800 From: Stanislav Fomichev To: Breno Leitao Cc: David Ahern , Ido Schimmel , "David S. Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , John Fastabend , Stanislav Fomichev , Shuah Khan , Eric Dumazet , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, david.laight.linux@gmail.com, kernel-team@meta.com Subject: Re: [PATCH net-next v4 2/7] net: cap sockopt_expand_out() at MAX_RW_COUNT Message-ID: References: <20261103-sockopt_expand_out_v2-v4-0-2d36da923578@debian.org> <20261103-sockopt_expand_out_v2-v4-2-2d36da923578@debian.org> X-Mailing-List: linux-kernel@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-Disposition: inline In-Reply-To: <20261103-sockopt_expand_out_v2-v4-2-2d36da923578@debian.org> On 11/03, Breno Leitao wrote: > sockopt_expand_out() grows the output iterator up to INT_MAX, but the > MCAST_MSFILTER getters converted by the next two patches rewind it with > iov_iter_revert() once they know the real reply size. iov_iter_revert() > refuses to unroll past MAX_RW_COUNT: > > if (WARN_ON(unroll > MAX_RW_COUNT)) > return; > > MAX_RW_COUNT is INT_MAX rounded down to a page boundary, so a caller > that expands into the (MAX_RW_COUNT, INT_MAX] range and then reverts > hits that WARN_ON, and the iterator is left where it was instead of > rewound. So does a caller whose optlen already covers such a size. > > Cap the size at MAX_RW_COUNT instead, before the early return for an > optlen that already covers it, so a size that could never be reverted > later is rejected up front. > > Sashiko found this while reviewing the conversions. > > Acked-by: Ido Schimmel > Signed-off-by: Breno Leitao Acked-by: Stanislav Fomichev