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[2001:8b0:1d0::2]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-475dd374e41sm203109415e9.12.2025.10.28.09.00.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Oct 2025 09:00:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1761667245; x=1762272045; darn=nongnu.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=3VO5d5EAGo4wZzbvR3QkkqwC3BxWJb1UbGxi7v8NEQc=; b=kbEKguJmxspj9Yi7+1gTZ2seffz5uK1/a5R/FEfskQbd9klxcHDNmf5K0uSyUBmALO T2/DRgvpxQ1S19bI+oB75JC2xSZ89zRZquRpHMZskcx+z+AeR7POFBZhyDaa6W4+eiV4 4LQccAxDIKieNukBkrtn0E08AFOu6zxPugM0mIYWA7mYMxASF0Lo8JWY253zFdLkK4oZ yH0a2z1LqahexfKw3gmfGfGbsqRG3WeViBCgGNEDRghK4lXWT59Au8j/0kBPUSencJPa Fnrth2zoTZol2kTMzaPE3Icw9EJHwdV3uJs10uHXgZ2e4GjRzpvvj2pWj0G4Tg6GgZj/ 0Utg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761667245; x=1762272045; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=3VO5d5EAGo4wZzbvR3QkkqwC3BxWJb1UbGxi7v8NEQc=; b=tKCLziRDB78Sx2jUn5WoiagILfZHgyHB6wR5g3YT7p54ec6zKV1qaVTMafuTe8qNIx SkAB8zo13SsM1DgeLsz12BFrwVPWZLv3IoeeZojUZxcdH/K4+zT7jqF6aXSLDG+b3ekN In79KxaaV/4T4yzLHI/fVpdVKBnW5MTJD0V9ar8yy9SeuebgZEbr3xkgRaBKefvrHOeQ c2hdVIdURJzTCtVi7FlIPGmzox2AnBAySqvdwjgsG2hNX8dmgnCJbbPeWthuDsbWj7m/ HWH4TLtJG8IlKfaiaoHtOB6xQFSzGN/sVOB5Mw7EbzsNZQ7F1RhFap6rVM0tZ1SnafdH uuSw== X-Gm-Message-State: AOJu0YzU+4f3e12e7XqppnNn27LSu9EtuRw8lH3J2JXdiDNR+UwUPq/L MD/aP1imE9IAO7CPxIJ16oYJkDIQ97TjOFUE0sYD380YrTHmt+EJ4zuIxdT5ZxlHZudkytk4N1j h/Me8 X-Gm-Gg: ASbGncu/0zVL1J24AFwJtpYqFsH4RlPNXSFfCoBftzzDKtqHcwxeeM4roUm/OGe46Zz DUkn+W8UhSt09u1U0j7WaD0PvdYDpwJKBpyz4rnoD09B8lT9knwnaPwv7F3Ef58AgL3N5k3NOJX xCr0niT5NUwwm07ZIb8F0Vak4zxCtdQJjso4u+uGU6wV7ZSeQ2Eo2j6WwUkfP9tOg6yO9SSaz0H 2au8EOPgQlW70FVG/yl2JKJanzOc9OzCm7eBFI0gldPiqxm+5L9v/8JDs8PRtXSvPJak1j9a/Tz I8+2FRmnMBQBQEStHQ5C58gLqrGrcO8TmadB+LL/gKs1KsicjnNhTlW8XbDw27HR3O9QzMz+600 BE5DGU8duIKy4r+t4JdQstegMfI9Oufd6P/DY01YgWbWIYwHM/o7zgBwKdeaZfXULsHx6fwS1Gv VlFkYc5Q== X-Google-Smtp-Source: AGHT+IFdEtd5mJn9ZwQUZlpnXD92xDMsuSzMIzWn+tbykOL4nXzE/Ma63P2HlZrSZlO2xnBG8pGDAA== X-Received: by 2002:a05:600c:3d8b:b0:471:1d8e:3c4f with SMTP id 5b1f17b1804b1-47717e4147cmr26891775e9.24.1761667245135; Tue, 28 Oct 2025 09:00:45 -0700 (PDT) From: Peter Maydell To: qemu-devel@nongnu.org Cc: Jason Wang , Bin Meng Subject: [PATCH] net: pad packets to minimum length in qemu_receive_packet() Date: Tue, 28 Oct 2025 16:00:42 +0000 Message-ID: <20251028160042.3321933-1-peter.maydell@linaro.org> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 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::330; envelope-from=peter.maydell@linaro.org; helo=mail-wm1-x330.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: 1761667431330154100 Content-Type: text/plain; charset="utf-8" In commits like 969e50b61a28 ("net: Pad short frames to minimum size before sending from SLiRP/TAP") we switched away from requiring network devices to handle short frames to instead having the net core code do the padding of short frames out to the ETH_ZLEN minimum size. We then dropped the code for handling short frames from the network devices in a series of commits like 140eae9c8f7 ("hw/net: e1000: Remove the logic of padding short frames in the receive path"). This missed one route where the device's receive code can still see a short frame: if the device is in loopback mode and it transmits a short frame via the qemu_receive_packet() function, this will be fed back into its own receive code without being padded. Add the padding logic to qemu_receive_packet(). This fixes a buffer overrun which can be triggered in the e1000_receive_iov() logic via the loopback code path. Other devices that use qemu_receive_packet() to implement loopback are cadence_gem, dp8393x, lan9118, msf2-emac, pcnet, rtl8139 and sungem. Cc: qemu-stable@nongnu.org Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3043 Signed-off-by: Peter Maydell Reviewed-by: Akihiko Odaki Reviewed-by: Philippe Mathieu-Daud=C3=A9 --- I think this is the right fix, but I'm not very familiar with the net internals... --- net/net.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/net/net.c b/net/net.c index 27e0d278071..8aefdb3424f 100644 --- a/net/net.c +++ b/net/net.c @@ -775,10 +775,20 @@ ssize_t qemu_send_packet(NetClientState *nc, const ui= nt8_t *buf, int size) =20 ssize_t qemu_receive_packet(NetClientState *nc, const uint8_t *buf, int si= ze) { + uint8_t min_pkt[ETH_ZLEN]; + size_t min_pktsz =3D sizeof(min_pkt); + if (!qemu_can_receive_packet(nc)) { return 0; } =20 + if (net_peer_needs_padding(nc)) { + if (eth_pad_short_frame(min_pkt, &min_pktsz, buf, size)) { + buf =3D min_pkt; + size =3D min_pktsz; + } + } + return qemu_net_queue_receive(nc->incoming_queue, buf, size); } =20 --=20 2.43.0