From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B22A6381AE4; Fri, 7 Aug 2026 15:09:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786115381; cv=none; b=VWhBgHIdqEH3h6mwcUNqcNRBXn9fYweTPKWoJpEooRzIqKVbqs4V/IkkAOjQYuEiqQbkrcpSmr+k9qK4S3ePCf6sQoFwDa97BgD0FuAJUQgNO4jVrb7DCXZg4kHK236b8LF0VK8eDkTK7+HfmM66vk/c38HAd1cc6wxuylY+xXk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786115381; c=relaxed/simple; bh=mb2I7FXBipUc8X8rlGI79//xH+l8Sl7tb49Ryz2fxdk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RPSwA0V+rONKFHDQ+h04fj1GtJQOC9spbGfPj/pbQWot4AhTEqK3SfLOzNpcvZ0zNT+OQwT5dNqG/J5adBt/PWh1yeqBrZX3xIPZULCAuXuqhi1pzw7fAIcrQ8WzPyjbzMQnuAf7o9filrvIy7VyVTT1oFqLzdLu+zFJiYYGfNM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vnXtx07G; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vnXtx07G" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F9841F000E9; Fri, 7 Aug 2026 15:09:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786115379; bh=aVcQTOZUpvyZbe8TbDj4XXFpAGdqz59OO/E5BgaaERc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=vnXtx07Gc1ectrNPe9czwd9y2gfwyOPiUfsW9hxfvayp/DJ1T5bNYB0xhQEKy7hDs htGIrpkJM8gglVsPfJnV4Rdk2o6QfQk04qOjFYDVDonDpThIluUzKGTA6Ef3RfoSRs i2Smy8wTcqh7WXIAYWq/IKCU2/o2CJ0i/H8JQ3+Q= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chris Gellermann , "David Hildenbrand (arm)" , Lorenzo Stoakes , Christian Brauner , "Liam R. Howlett" , Michal Hocko , Mike Rapoport , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , Andrew Morton Subject: [PATCH 6.18 256/396] selftests/clone3: fix wild pointer access of getline due to missing init Date: Fri, 7 Aug 2026 16:36:56 +0200 Message-ID: <20260807143429.770751335@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807143424.272339768@linuxfoundation.org> References: <20260807143424.272339768@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Gellermann commit 8f6f9fd93cd7a5dd607ad5cd910476dd68fff3ed upstream. Patch series "selftests: Add missing initalization of pointer passed to getline", v2. This patch (of 2): Clone3_set_tid uses getline(&line, ...) in a loop to read the child's process status. The code expects that getline allocates the buffer for the line on the first loop iteration. According to the Open Group Spec[1], char *line has to be null pointer for this: > ssize_t getline(char **restrict lineptr, ...); > If *lineptr is a null pointer or if the object pointed to by *lineptr > is of insufficient size, an object shall be allocated as if by malloc() > or the object shall be reallocated as if by realloc()[...]. However, char *line is only declared, leading to an undefined value that is potentially non-null. In an example run with Musl v1.2.6, the realloc call[2] of getdelim, which implements getline, triggers a segfault: ./run_kselftest.sh --test clone3:clone3_set_tid [ 1366.165898] kselftest: Running tests in clone3 ... [ 1367.799244] clone3_set_tid[811]: unhandled signal 11 code 0x1 at 0x0000000000000000 in libc.so[68184,3fbf69f000+4c000] [ 1367.802808] CPU: 0 UID: 0 PID: 811 Comm: clone3_set_tid Not tainted .. [ 1367.804188] epc: 0x0000003fbf6b0184 [ 1367.804188] ra : 0x0000003fbf6d4664 [ 1367.804188] sp : 0x0000003fce5f2e40 [ 1367.805314] gp : 0x0000002aaab0dfb8 [ 1367.805314] tp : 0x0000003fbf6f14a8 [ 1367.805314] t0 : 0x0000003fbf63d000 ... Looking at the realloc implementation, Musl mallocs for a null pointer memory. But for a non-null pointer, it assumes it's passed a valid pointer to the heap and tries to access its meta-data. This leads to the segfault we see: void *realloc(void *p, size_t n) { if (!p) return malloc(n); if (size_overflows(n)) return 0; struct meta *g = get_meta(p); ... } Fix this by properly initializing the line pointer to NULL. Link: https://lore.kernel.org/20260722130246.2135563-1-christian.gellermann@codasip.com Link: https://lore.kernel.org/20260722130246.2135563-2-christian.gellermann@codasip.com Link: https://pubs.opengroup.org/onlinepubs/9799919799/functions/getline.html [1] Link: https://git.musl-libc.org/cgit/musl/tree/src/stdio/getdelim.c#n38 [2] Fixes: 41585bbeeef9 ("selftests: add tests for clone3() with *set_tid") Signed-off-by: Chris Gellermann Acked-by: David Hildenbrand (arm) Reviewed-by: Lorenzo Stoakes Cc: Christian Brauner Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- tools/testing/selftests/clone3/clone3_set_tid.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/tools/testing/selftests/clone3/clone3_set_tid.c +++ b/tools/testing/selftests/clone3/clone3_set_tid.c @@ -141,7 +141,7 @@ int main(int argc, char *argv[]) { FILE *f; char buf; - char *line; + char *line = NULL; int status; int ret = -1; size_t len = 0;