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Mon, 18 Nov 2024 04:47:59 -0800 (PST) From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= To: qemu-devel@nongnu.org Cc: Peter Maydell , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Subject: [PULL 13/15] hw/net/virtio-net.c: Don't assume IP length field is aligned Date: Mon, 18 Nov 2024 13:46:40 +0100 Message-ID: <20241118124643.6958-14-philmd@linaro.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20241118124643.6958-1-philmd@linaro.org> References: <20241118124643.6958-1-philmd@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::433; envelope-from=philmd@linaro.org; helo=mail-wr1-x433.google.com 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1731934170895116600 From: Peter Maydell In virtio-net.c we assume that the IP length field in the packet is aligned, and we copy its address into a uint16_t* in the VirtioNetRscUnit struct which we then dereference later. This isn't a safe assumption; it will also result in compilation failures if we mark the ip_header struct as QEMU_PACKED because the compiler will not let you take the address of an unaligned struct field. Make the ip_plen field in VirtioNetRscUnit a void*, and make all the places where we read or write through that pointer instead use some new accessor functions read_unit_ip_len() and write_unit_ip_len() which account for the pointer being potentially unaligned and also do the network-byte-order conversion we were previously using htons() to perform. Signed-off-by: Peter Maydell Reviewed-by: Philippe Mathieu-Daud=C3=A9 Message-ID: <20241114141619.806652-2-peter.maydell@linaro.org> Signed-off-by: Philippe Mathieu-Daud=C3=A9 --- include/hw/virtio/virtio-net.h | 2 +- hw/net/virtio-net.c | 23 +++++++++++++++++++---- 2 files changed, 20 insertions(+), 5 deletions(-) diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h index 060c23c04d..b9ea9e824e 100644 --- a/include/hw/virtio/virtio-net.h +++ b/include/hw/virtio/virtio-net.h @@ -102,7 +102,7 @@ typedef struct VirtioNetRscStat { /* Rsc unit general info used to checking if can coalescing */ typedef struct VirtioNetRscUnit { void *ip; /* ip header */ - uint16_t *ip_plen; /* data len pointer in ip header field */ + void *ip_plen; /* pointer to unaligned uint16_t data len in ip header = */ struct tcp_header *tcp; /* tcp header */ uint16_t tcp_hdrlen; /* tcp header len */ uint16_t payload; /* pure payload without virtio/eth/ip/tcp */ diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index f2104ed364..75b4a28fb3 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -2049,6 +2049,21 @@ static ssize_t virtio_net_do_receive(NetClientState = *nc, const uint8_t *buf, return virtio_net_receive_rcu(nc, buf, size, false); } =20 +/* + * Accessors to read and write the IP packet data length field. This + * is a potentially unaligned network-byte-order 16 bit unsigned integer + * pointed to by unit->ip_len. + */ +static uint16_t read_unit_ip_len(VirtioNetRscUnit *unit) +{ + return lduw_be_p(unit->ip_plen); +} + +static void write_unit_ip_len(VirtioNetRscUnit *unit, uint16_t l) +{ + stw_be_p(unit->ip_plen, l); +} + static void virtio_net_rsc_extract_unit4(VirtioNetRscChain *chain, const uint8_t *buf, VirtioNetRscUnit *unit) @@ -2063,7 +2078,7 @@ static void virtio_net_rsc_extract_unit4(VirtioNetRsc= Chain *chain, unit->ip_plen =3D &ip->ip_len; unit->tcp =3D (struct tcp_header *)(((uint8_t *)unit->ip) + ip_hdrlen); unit->tcp_hdrlen =3D (htons(unit->tcp->th_offset_flags) & 0xF000) >> 1= 0; - unit->payload =3D htons(*unit->ip_plen) - ip_hdrlen - unit->tcp_hdrlen; + unit->payload =3D read_unit_ip_len(unit) - ip_hdrlen - unit->tcp_hdrle= n; } =20 static void virtio_net_rsc_extract_unit6(VirtioNetRscChain *chain, @@ -2082,7 +2097,7 @@ static void virtio_net_rsc_extract_unit6(VirtioNetRsc= Chain *chain, =20 /* There is a difference between payload length in ipv4 and v6, ip header is excluded in ipv6 */ - unit->payload =3D htons(*unit->ip_plen) - unit->tcp_hdrlen; + unit->payload =3D read_unit_ip_len(unit) - unit->tcp_hdrlen; } =20 static size_t virtio_net_rsc_drain_seg(VirtioNetRscChain *chain, @@ -2231,7 +2246,7 @@ static int32_t virtio_net_rsc_coalesce_data(VirtioNet= RscChain *chain, VirtioNetRscUnit *o_unit; =20 o_unit =3D &seg->unit; - o_ip_len =3D htons(*o_unit->ip_plen); + o_ip_len =3D read_unit_ip_len(o_unit); nseq =3D htonl(n_unit->tcp->th_seq); oseq =3D htonl(o_unit->tcp->th_seq); =20 @@ -2267,7 +2282,7 @@ coalesce: o_unit->payload +=3D n_unit->payload; /* update new data len */ =20 /* update field in ip header */ - *o_unit->ip_plen =3D htons(o_ip_len + n_unit->payload); + write_unit_ip_len(o_unit, o_ip_len + n_unit->payload); =20 /* Bring 'PUSH' big, the whql test guide says 'PUSH' can be coales= ced for windows guest, while this may change the behavior for linux --=20 2.45.2