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 B69E03C10A7; Tue, 21 Jul 2026 21:44:37 +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=1784670280; cv=none; b=tiABk68vXsT365F9FlorZGUvXA9RV+T6G76ZWSavqRuG7GSTl8I/neqtT5z4k1sAWNw7h4GbCFR/zX2c/23TO9SoST104d9/S2youFh+u5b5+IvbDm5yc/chj0hN/n9NRebPvIPcUk9IbvrzWxFRI+NA1yFRyiLcmfO4x7SSUsI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784670280; c=relaxed/simple; bh=XFlLVqt2w1gcgiwHyINrj/Ir0p8CoCclYftGjhTZRJE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AlI3VbZlFIeTkRHoNk5grX+AJDoSOBqHOz8Un67gs/4j/BBIbZGIZfGZv4lOn/pyJDu3Ln/UmeUS/zv+ZZ2MJ9QbmX0Qkvz6D4UrOcdT9YNeKw1M/psORW4kAztNNHBGjirFwhaEJ1sJADPkjcyuzebTQ9eMZY74Sq1AMaYU29k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=E9CKfiMQ; 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="E9CKfiMQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 231211F000E9; Tue, 21 Jul 2026 21:44:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784670277; bh=FxH4WXB9HWig1KGYWv4Dqw9fwvmTRg0XbUNOgud6Z3k=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=E9CKfiMQ3KOhUu0kUsLP4G7gQYF+Ll9vUJRqk4a5yy8jm9FlEeXnUlE0Zt4X+U+No qDQWyzrc65m+a5+jVZQG3TmYdIK4r6KifzrFBu7Cn5NO6HR0O1xfp3Gws+u6VMESH9 YZx+zuiJSW+eHjS4KnvjWrLWQij5xF8Uvxyvo8fg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zhan Xusheng , Thomas Gleixner Subject: [PATCH 6.1 0871/1067] posix-cpu-timers: Use u64 multiplication in update_rlimit_cpu() Date: Tue, 21 Jul 2026 17:24:32 +0200 Message-ID: <20260721152444.018856312@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152424.521567757@linuxfoundation.org> References: <20260721152424.521567757@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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zhan Xusheng commit 26aff38fefb1d6cd87e22525f41cc8f1aa61b24f upstream. update_rlimit_cpu() converts the RLIMIT_CPU value to nanoseconds with u64 nsecs = rlim_new * NSEC_PER_SEC; On 32-bit kernels both rlim_new (unsigned long) and NSEC_PER_SEC (1000000000L) are 32-bit, so the multiplication is performed in unsigned long and truncated for rlim_new > 4 seconds before being widened to u64. The same file already casts to u64 for the matching computation in check_process_timers(): u64 softns = (u64)soft * NSEC_PER_SEC; As a result, the truncated value is installed into the CPUCLOCK_PROF expiry cache (nextevt), causing the process CPU timer to be programmed to fire prematurely for any RLIMIT_CPU soft limit >= 5 seconds. The actual SIGXCPU/SIGKILL decision in check_process_timers() already casts to u64 and is therefore correct, so limit enforcement is not broken; only the expiry-cache programming is wrong. Apply the same cast here so both paths convert rlim_cur identically. 64-bit kernels are unaffected. Fixes: 858cf3a8c599 ("timers/itimer: Convert internal cputime_t units to nsec") Signed-off-by: Zhan Xusheng Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260616112017.1681372-1-zhanxusheng@xiaomi.com Signed-off-by: Greg Kroah-Hartman --- kernel/time/posix-cpu-timers.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -41,7 +41,7 @@ void posix_cputimers_group_init(struct p */ int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new) { - u64 nsecs = rlim_new * NSEC_PER_SEC; + u64 nsecs = (u64)rlim_new * NSEC_PER_SEC; unsigned long irq_fl; if (!lock_task_sighand(task, &irq_fl))