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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id m19-20020a05600c4f5300b003c6f3f6675bsm6044325wmq.26.2022.10.17.10.39.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Oct 2022 10:39:53 -0700 (PDT) Date: Mon, 17 Oct 2022 18:39:51 +0100 From: "Dr. David Alan Gilbert" To: Eric Blake Cc: qemu-devel@nongnu.org, Vladimir Sementsov-Ogievskiy , "open list:Network Block Dev..." Subject: Re: [PATCH] nbd/server: Use smarter assert Message-ID: References: <20221017173727.1246179-1-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221017173727.1246179-1-eblake@redhat.com> User-Agent: Mutt/2.2.7 (2022-08-07) Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.255, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Eric Blake (eblake@redhat.com) wrote: > Assigning strlen() to a uint32_t and then asserting that it isn't too > large doesn't catch the case of an input string 4G in length. > Thankfully, the incoming string can never be that large: if the export > name is reflecting what the client asked about, we already guarantee > that we drop the NBD connection if the client tries to send more than > 32M in a single NBD_OPT_* request; and if the export name is coming > from qemu, nbd_receive_negotiate() asserted that strlen(info->name) <= > NBD_MAX_STRING_SIZE. Still, it doesn't hurt to be more explicit in > how we write our assertion that we are aware that no wraparound is > possible. > > Fixes: 93676c88 ("nbd: Don't send oversize strings", v4.2.0) > Reported-by: Dr. David Alan Gilbert > Signed-off-by: Eric Blake Reviewed-by: Dr. David Alan Gilbert > --- > nbd/client.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/nbd/client.c b/nbd/client.c > index 60c9f4941a..b601ee97e5 100644 > --- a/nbd/client.c > +++ b/nbd/client.c > @@ -658,7 +658,7 @@ static int nbd_send_meta_query(QIOChannel *ioc, uint32_t opt, > char *p; > > data_len = sizeof(export_len) + export_len + sizeof(queries); > - assert(export_len <= NBD_MAX_STRING_SIZE); > + assert(strlen(export) <= NBD_MAX_STRING_SIZE); > if (query) { > query_len = strlen(query); > data_len += sizeof(query_len) + query_len; > -- > 2.37.3 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK