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Tue, 12 May 2020 13:49:42 +0000 (UTC) Subject: Re: Assertion failure through vring_split_desc_read To: Alexander Bulekov , qemu-devel@nongnu.org References: <20200511035124.v2ff4f5gyfh6xlgc@mozz.bu.edu> From: Laurent Vivier Autocrypt: addr=lvivier@redhat.com; prefer-encrypt=mutual; keydata= mQINBFYFJhkBEAC2me7w2+RizYOKZM+vZCx69GTewOwqzHrrHSG07MUAxJ6AY29/+HYf6EY2 WoeuLWDmXE7A3oJoIsRecD6BXHTb0OYS20lS608anr3B0xn5g0BX7es9Mw+hV/pL+63EOCVm SUVTEQwbGQN62guOKnJJJfphbbv82glIC/Ei4Ky8BwZkUuXd7d5NFJKC9/GDrbWdj75cDNQx UZ9XXbXEKY9MHX83Uy7JFoiFDMOVHn55HnncflUncO0zDzY7CxFeQFwYRbsCXOUL9yBtqLer Ky8/yjBskIlNrp0uQSt9LMoMsdSjYLYhvk1StsNPg74+s4u0Q6z45+l8RAsgLw5OLtTa+ePM JyS7OIGNYxAX6eZk1+91a6tnqfyPcMbduxyBaYXn94HUG162BeuyBkbNoIDkB7pCByed1A7q q9/FbuTDwgVGVLYthYSfTtN0Y60OgNkWCMtFwKxRaXt1WFA5ceqinN/XkgA+vf2Ch72zBkJL RBIhfOPFv5f2Hkkj0MvsUXpOWaOjatiu0fpPo6Hw14UEpywke1zN4NKubApQOlNKZZC4hu6/ 8pv2t4HRi7s0K88jQYBRPObjrN5+owtI51xMaYzvPitHQ2053LmgsOdN9EKOqZeHAYG2SmRW LOxYWKX14YkZI5j/TXfKlTpwSMvXho+efN4kgFvFmP6WT+tPnwARAQABtCNMYXVyZW50IFZp dmllciA8bHZpdmllckByZWRoYXQuY29tPokCOAQTAQIAIgUCVgVQgAIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQ8ww4vT8vvjwpgg//fSGy0Rs/t8cPFuzoY1cex4limJQfReLr SJXCANg9NOWy/bFK5wunj+h/RCFxIFhZcyXveurkBwYikDPUrBoBRoOJY/BHK0iZo7/WQkur 6H5losVZtrotmKOGnP/lJYZ3H6OWvXzdz8LL5hb3TvGOP68K8Bn8UsIaZJoeiKhaNR0sOJyI YYbgFQPWMHfVwHD/U+/gqRhD7apVysxv5by/pKDln1I5v0cRRH6hd8M8oXgKhF2+rAOL7gvh jEHSSWKUlMjC7YwwjSZmUkL+TQyE18e2XBk85X8Da3FznrLiHZFHQ/NzETYxRjnOzD7/kOVy gKD/o7asyWQVU65mh/ECrtjfhtCBSYmIIVkopoLaVJ/kEbVJQegT2P6NgERC/31kmTF69vn8 uQyW11Hk8tyubicByL3/XVBrq4jZdJW3cePNJbTNaT0d/bjMg5zCWHbMErUib2Nellnbg6bc 2HLDe0NLVPuRZhHUHM9hO/JNnHfvgiRQDh6loNOUnm9Iw2YiVgZNnT4soUehMZ7au8PwSl4I KYE4ulJ8RRiydN7fES3IZWmOPlyskp1QMQBD/w16o+lEtY6HSFEzsK3o0vuBRBVp2WKnssVH qeeV01ZHw0bvWKjxVNOksP98eJfWLfV9l9e7s6TaAeySKRRubtJ+21PRuYAxKsaueBfUE7ZT 7ze0LUxhdXJlbnQgVml2aWVyIChSZWQgSGF0KSA8bHZpdmllckByZWRoYXQuY29tPokCOAQT AQIAIgUCVgUmGQIbAwYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQ8ww4vT8vvjxtNBAA o2xGmbXl9vJQALkj7MVlsMlgewQ1rdoZl+bZ6ythTSBsqwwtl1BUTQGA1GF2LAchRVYca5bJ lw4ai5OdZ/rc5dco2XgrRFtj1np703BzNEhGU1EFxtms/Y9YOobq/GZpck5rK8jV4osEb8oc 3xEgCm/xFwI/2DOe0/s2cHKzRkvdmKWEDhT1M+7UhtSCnloX776zCsrofYiHP2kasFyMa/5R 9J1Rt9Ax/jEAX5vFJ8+NPf68497nBfrAtLM3Xp03YJSr/LDxer44Mevhz8dFw7IMRLhnuSfr 8jP93lr6Wa8zOe3pGmFXZWpNdkV/L0HaeKwTyDKKdUDH4U7SBnE1gcDfe9x08G+oDfVhqED8 qStKCxPYxRUKIdUjGPF3f5oj7N56Q5zZaZkfxeLNTQ13LDt3wGbVHyZxzFc81B+qT8mkm74y RbeVSuviPTYjbBQ66GsUgiZZpDUyJ6s54fWqQdJf4VFwd7M/mS8WEejbSjglGHMxMGiBeRik Y0+ur5KAF7z0D1KfW1kHO9ImQ0FbEbMbTMf9u2+QOCrSWOz/rj23EwPrCQ2TSRI2fWakMJZ+ zQZvy+ei3D7lZ09I9BT/GfFkTIONgtNfDxwyMc4v4XyP0IvvZs/YZqt7j3atyTZM0S2HSaZ9 rXmQYkBt1/u691cZfvy+Tr2xZaDpFcjPkci5Ag0EVgUmGQEQALxSQRbl/QOnmssVDxWhHM5T Gxl7oLNJms2zmBpcmlrIsn8nNz0rRyxT460k2niaTwowSRK8KWVDeAW6ZAaWiYjLlTunoKwv F8vP3JyWpBz0diTxL5o+xpvy/Q6YU3BNefdq8Vy3rFsxgW7mMSrI/CxJ667y8ot5DVugeS2N yHfmZlPGE0Nsy7hlebS4liisXOrN3jFzasKyUws3VXek4V65lHwB23BVzsnFMn/bw/rPliqX Gcwl8CoJu8dSyrCcd1Ibs0/Inq9S9+t0VmWiQWfQkz4rvEeTQkp/VfgZ6z98JRW7S6l6eoph oWs0/ZyRfOm+QVSqRfFZdxdP2PlGeIFMC3fXJgygXJkFPyWkVElr76JTbtSHsGWbt6xUlYHK XWo+xf9WgtLeby3cfSkEchACrxDrQpj+Jt/JFP+q997dybkyZ5IoHWuPkn7uZGBrKIHmBunT co1+cKSuRiSCYpBIXZMHCzPgVDjk4viPbrV9NwRkmaOxVvye0vctJeWvJ6KA7NoAURplIGCq kCRwg0MmLrfoZnK/gRqVJ/f6adhU1oo6z4p2/z3PemA0C0ANatgHgBb90cd16AUxpdEQmOCm dNnNJF/3Zt3inzF+NFzHoM5Vwq6rc1JPjfC3oqRLJzqAEHBDjQFlqNR3IFCIAo4SYQRBdAHB CzkM4rWyRhuVABEBAAGJAh8EGAECAAkFAlYFJhkCGwwACgkQ8ww4vT8vvjwg9w//VQrcnVg3 TsjEybxDEUBm8dBmnKqcnTBFmxN5FFtIWlEuY8+YMiWRykd8Ln9RJ/98/ghABHz9TN8TRo2b 6WimV64FmlVn17Ri6FgFU3xNt9TTEChqAcNg88eYryKsYpFwegGpwUlaUaaGh1m9OrTzcQy+ klVfZWaVJ9Nw0keoGRGb8j4XjVpL8+2xOhXKrM1fzzb8JtAuSbuzZSQPDwQEI5CKKxp7zf76 J21YeRrEW4WDznPyVcDTa+tz++q2S/BpP4W98bXCBIuQgs2m+OflERv5c3Ojldp04/S4NEjX EYRWdiCxN7ca5iPml5gLtuvhJMSy36glU6IW9kn30IWuSoBpTkgV7rLUEhh9Ms82VWW/h2Tx L8enfx40PrfbDtWwqRID3WY8jLrjKfTdR3LW8BnUDNkG+c4FzvvGUs8AvuqxxyHbXAfDx9o/ jXfPHVRmJVhSmd+hC3mcQ+4iX5bBPBPMoDqSoLt5w9GoQQ6gDVP2ZjTWqwSRMLzNr37rJjZ1 pt0DCMMTbiYIUcrhX8eveCJtY7NGWNyxFCRkhxRuGcpwPmRVDwOl39MB3iTsRighiMnijkbL XiKoJ5CDVvX5yicNqYJPKh5MFXN1bvsBkmYiStMRbrD0HoY1kx5/VozBtc70OU0EB8Wrv9hZ D+Ofp0T3KOr1RUHvCZoLURfFhSQ= Message-ID: Date: Tue, 12 May 2020 15:49:41 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200511035124.v2ff4f5gyfh6xlgc@mozz.bu.edu> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=lvivier@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/12 01:41:59 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, 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_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Stefan Hajnoczi , "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 11/05/2020 05:51, Alexander Bulekov wrote: > Hello, > While fuzzing, I found an input that triggers an assertion failure > through virtio-rng -> vring_split_desc_read. Maybe this is related to: > Message-ID: <20200511033001.dzvtbdhl3oz5pgiy@mozz.bu.edu> > Assertion failure through virtio_lduw_phys_cached > > #8 0x7fe6a9acf091 in __assert_fail /build/glibc-GwnBeO/glibc-2.30/assert/assert.c:101:3 > #9 0x564cbe7d96fd in address_space_read_cached include/exec/memory.h:2423:5 > #10 0x564cbe7e79c5 in vring_split_desc_read hw/virtio/virtio.c:236:5 > #11 0x564cbe7e84ce in virtqueue_split_read_next_desc hw/virtio/virtio.c:929:5 > #12 0x564cbe78f86b in virtqueue_split_get_avail_bytes hw/virtio/virtio.c:1009:18 > #13 0x564cbe78ab22 in virtqueue_get_avail_bytes hw/virtio/virtio.c:1208:9 > #14 0x564cc08aade1 in get_request_size hw/virtio/virtio-rng.c:40:5 > #15 0x564cc08aa20b in virtio_rng_process hw/virtio/virtio-rng.c:115:12 > #16 0x564cc08a8c48 in virtio_rng_set_status hw/virtio/virtio-rng.c:172:5 > #17 0x564cbe7a50be in virtio_set_status hw/virtio/virtio.c:1876:9 > #18 0x564cc08d1b8f in virtio_pci_common_write hw/virtio/virtio-pci.c:1245:9 > > I can reproduce it in a qemu 5.0 build using these qtest commands: > https://paste.debian.net/plain/1146089 > (not including them here, as some are quite long) > > wget https://paste.debian.net/plain/1146089 -O qtest-trace; ~/Development/qemu/build/i386-softmmu/qemu-system-i386 -M pc-q35-5.0 -device virtio-rng-pci,addr=04.0 -display none -nodefaults -nographic -qtest stdio < qtest-trace Nice work. If I use directly "curl https://paste.debian.net/plain/1146089 | qemu-system-i386 ..." I have only a warning: qemu-system-i386: Guest moved used index from 0 to 496 I've added some traces. The assert is triggered because addr (0xffff0) >= cache->len (0x11d0). addr is 2nd argument of: address_space_read_cached(cache, i * sizeof(VRingDesc), desc, sizeof(VRingDesc)); and "i" appears to be "65535". In virtqueue_split_read_next_desc(), the value is checked not to be greater than max. But max is 268345360... "max" is provided by virtqueue_split_get_avail_bytes(), it's originally vq->vring.num (255), but in the case of VRING_DESC_F_INDIRECT max is updated to "desc.len / sizeof(VRingDesc)". desc.len is 4293525760. It is set from max to cache->len by address_space_cache_init() but this value seems to be truncated in the next iteration of the loop (where we have the assert()). I'm investigating why we have that. Thanks, Laurent