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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1750228302; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=esen0C5DF8gqMNpYt5xxCSW6Q2tYtqV4xzl7dx+1CEA=; b=hVqIBfOcJMdSSJ8aXARoi2mgkeX4BrKraPsJd3HZJmquw9gqXe5WD0/VooN8kDwil7Dsh1 yLt6p/4Jl/34D5Wn7HXEi6zwLmSoRgE1OHQDKo04E69se0qSpwFMOw9BsFfPyz5DtYSDHJ 9U0HQ/cgvLj7Chvp+7DGdYbhLRZmXXk= X-MC-Unique: p8OAyM8aMrqoSfCo2YAvPQ-1 X-Mimecast-MFC-AGG-ID: p8OAyM8aMrqoSfCo2YAvPQ_1750228299 To: devel@lists.libvirt.org Subject: [PATCH] virSocketAddrPrefixToNetmask: Prevent undefined behaviour on bitshifts on signed integer Date: Wed, 18 Jun 2025 08:31:36 +0200 Message-ID: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 4NREHwhEY-QpGfKVBfWmweawNnpjkSImxsEzAjcSzbI_1750228299 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Message-ID-Hash: OGO2J3IWD5Y4Z7Q7O3ZIBWQTQ3J5W6TK X-Message-ID-Hash: OGO2J3IWD5Y4Z7Q7O3ZIBWQTQ3J5W6TK X-MailFrom: pkrempa@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-config-1; header-match-config-2; header-match-config-3; header-match-devel.lists.libvirt.org-0; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; suspicious-header X-Mailman-Version: 3.2.2 Precedence: list List-Id: Development discussions about the libvirt library & tools Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: From: Peter Krempa via Devel Reply-To: Peter Krempa X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1750228338221116600 Content-Type: text/plain; charset="utf-8" From: Peter Krempa Shifting bits into the sign bit is undefined behaviour in C although both gcc and clang handle it as expected. Since the value is used as unsigned convert it to unsigned int. For code readability use 'if' statement instead of a ternary. Closes: https://gitlab.com/libvirt/libvirt/-/issues/785 Signed-off-by: Peter Krempa Reviewed-by: Pavel Hrdina --- src/util/virsocketaddr.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/util/virsocketaddr.c b/src/util/virsocketaddr.c index a2e6701670..f53768878e 100644 --- a/src/util/virsocketaddr.c +++ b/src/util/virsocketaddr.c @@ -1144,12 +1144,14 @@ virSocketAddrPrefixToNetmask(unsigned int prefix, netmask->data.stor.ss_family =3D AF_UNSPEC; /* assume failure */ if (family =3D=3D AF_INET) { - int ip; + unsigned int ip =3D 0; if (prefix > 32) return -1; - ip =3D prefix ? ~((1 << (32 - prefix)) - 1) : 0; + if (prefix > 0) + ip =3D ~((1U << (32 - prefix)) - 1); + netmask->data.inet4.sin_addr.s_addr =3D htonl(ip); netmask->data.stor.ss_family =3D AF_INET; netmask->len =3D sizeof(struct sockaddr_in); --=20 2.49.0