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GET /api/patches/2196613/?format=api
{ "id": 2196613, "url": "http://patchwork.ozlabs.org/api/patches/2196613/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-um/patch/20260215142803.1455757-1-maci.stgn@gmail.com/", "project": { "id": 60, "url": "http://patchwork.ozlabs.org/api/projects/60/?format=api", "name": "User-mode Linux Development", "link_name": "linux-um", "list_id": "linux-um.lists.infradead.org", "list_email": "linux-um@lists.infradead.org", "web_url": "", "scm_url": "", "webscm_url": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260215142803.1455757-1-maci.stgn@gmail.com>", "list_archive_url": null, "date": "2026-02-15T14:28:02", "name": "[1/2] um: fix address-of CMSG_DATA() rvalue in stub", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "194d91c21a8e07fd5b91f89bc98994962cb1ff06", "submitter": { "id": 92646, "url": "http://patchwork.ozlabs.org/api/people/92646/?format=api", "name": "Marcel W. Wysocki", "email": "maci.stgn@gmail.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linux-um/patch/20260215142803.1455757-1-maci.stgn@gmail.com/mbox/", "series": [ { "id": 492220, "url": "http://patchwork.ozlabs.org/api/series/492220/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-um/list/?series=492220", "date": "2026-02-15T14:28:03", "name": "[1/2] um: fix address-of CMSG_DATA() rvalue in stub", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/492220/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2196613/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2196613/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linux-um-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n secure) header.d=lists.infradead.org header.i=@lists.infradead.org\n header.a=rsa-sha256 header.s=bombadil.20210309 header.b=GqVmnokF;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20230601 header.b=d2YYEMA2;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=none (no SPF record) smtp.mailfrom=lists.infradead.org\n (client-ip=2607:7c80:54:3::133; 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Wysocki\" <maci.stgn@gmail.com>", "To": "Richard Weinberger <richard@nod.at>,\n\tAnton Ivanov <anton.ivanov@cambridgegreys.com>,\n\tJohannes Berg <johannes@sipsolutions.net>", "Cc": "linux-um@lists.infradead.org,\n\tlinux-kernel@vger.kernel.org,\n\t\"Marcel W . Wysocki\" <maci.stgn@gmail.com>", "Subject": "[PATCH 1/2] um: fix address-of CMSG_DATA() rvalue in stub", "Date": "Sun, 15 Feb 2026 22:28:02 +0800", "Message-ID": "<20260215142803.1455757-1-maci.stgn@gmail.com>", "X-Mailer": "git-send-email 2.53.0", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "X-CRM114-Version": "20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 ", "X-CRM114-CacheID": "sfid-20260215_062819_668208_BEF956A5 ", "X-CRM114-Status": "GOOD ( 14.73 )", "X-Spam-Score": "-2.1 (--)", "X-Spam-Report": "Spam detection software,\n running on the system \"bombadil.infradead.org\",\n has NOT identified this incoming email as spam. The original\n message has been attached to this so you can view it or label\n similar future email. If you have any questions, see\n the administrator of that system for details.\n Content preview: The UML stub takes the address of CMSG_DATA(fd_msg): fd_map\n = (void *)&CMSG_DATA(fd_msg); CMSG_DATA() is specified by POSIX to return\n unsigned char *. Taking its address is semantically wrong -- the intent is\n to get a pointer to the control message data,\n which is exactly what CMSG_DATA()\n a [...]\n Content analysis details: (-2.1 points, 5.0 required)\n pts rule name description\n ---- ----------------------\n --------------------------------------------------\n -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no\n trust\n [2607:f8b0:4864:20:0:0:0:52f listed in]\n [list.dnswl.org]\n 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record\n -0.0 SPF_PASS SPF: sender matches SPF record\n -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from\n author's\n domain\n -0.1 DKIM_VALID Message has at least one valid DKIM or DK\n signature\n 0.1 DKIM_SIGNED Message has a DKIM or DK signature,\n not necessarily valid\n -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from\n envelope-from domain\n -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1%\n [score: 0.0000]\n 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail\n provider\n [maci.stgn(at)gmail.com]", "X-BeenThere": "linux-um@lists.infradead.org", "X-Mailman-Version": "2.1.34", "Precedence": "list", "List-Id": "<linux-um.lists.infradead.org>", "List-Unsubscribe": "<http://lists.infradead.org/mailman/options/linux-um>,\n <mailto:linux-um-request@lists.infradead.org?subject=unsubscribe>", "List-Archive": "<http://lists.infradead.org/pipermail/linux-um/>", "List-Post": "<mailto:linux-um@lists.infradead.org>", "List-Help": "<mailto:linux-um-request@lists.infradead.org?subject=help>", "List-Subscribe": "<http://lists.infradead.org/mailman/listinfo/linux-um>,\n <mailto:linux-um-request@lists.infradead.org?subject=subscribe>", "Sender": "\"linux-um\" <linux-um-bounces@lists.infradead.org>", "Errors-To": "linux-um-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org" }, "content": "The UML stub takes the address of CMSG_DATA(fd_msg):\n\n fd_map = (void *)&CMSG_DATA(fd_msg);\n\nCMSG_DATA() is specified by POSIX to return unsigned char *. Taking\nits address is semantically wrong -- the intent is to get a pointer\nto the control message data, which is exactly what CMSG_DATA()\nalready returns.\n\nThis happens to compile with glibc because glibc's primary\nCMSG_DATA definition accesses a flexible array member:\n\n #define CMSG_DATA(cmsg) ((cmsg)->__cmsg_data)\n\nAn array lvalue can have its address taken, and &array yields the\nsame address as array. However, glibc also has an alternative\ndefinition that uses pointer arithmetic (returning an rvalue), and\nmusl's definition always uses pointer arithmetic:\n\n /* musl */\n #define CMSG_DATA(cmsg) \\\n ((unsigned char *)(((struct cmsghdr *)(cmsg)) + 1))\n\nTaking the address of an rvalue is a hard error in C, so the\ncurrent code fails to compile with musl libc.\n\nRemove the erroneous & operator. The resulting code is correct\nregardless of the CMSG_DATA implementation -- it simply assigns the\ndata pointer, which is what the subsequent code (fd_map[--num_fds])\nexpects.\n\nNo functional change with glibc; fixes the build with musl.\n\nSigned-off-by: Marcel W. Wysocki <maci.stgn@gmail.com>\n---\n arch/um/kernel/skas/stub.c | 2 +-\n 1 file changed, 1 insertion(+), 1 deletion(-)", "diff": "diff --git a/arch/um/kernel/skas/stub.c b/arch/um/kernel/skas/stub.c\n--- a/arch/um/kernel/skas/stub.c\n+++ b/arch/um/kernel/skas/stub.c\n@@ -146,7 +146,7 @@\n \t\t/* Receive the FDs */\n \t\tnum_fds = 0;\n \t\tfd_msg = msghdr.msg_control;\n-\t\tfd_map = (void *)&CMSG_DATA(fd_msg);\n+\t\tfd_map = (void *)CMSG_DATA(fd_msg);\n \t\tif (res == iov.iov_len && msghdr.msg_controllen > sizeof(struct cmsghdr))\n \t\t\tnum_fds = (fd_msg->cmsg_len - CMSG_LEN(0)) / sizeof(int);\n \n", "prefixes": [ "1/2" ] }