From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 9A04F325736; Tue, 16 Dec 2025 12:13:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765887204; cv=none; b=lkF9xSwuQAo+D4bY1fYxoFrf0Cx0gVXGpe+nRieTl1apZjrUkbwuTljZ3MJZdpPMBGtbULgxCoLnl1E/j7EaBQ4aKP92BiIqX8CuelZrZlieekSfuqQYtzQK/knHZF+LvcLiHG/AS+qMQzoi6pdK3dgyaC8KAfBv257IE3xL10s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765887204; c=relaxed/simple; bh=yDiQO3+he43LRnEhUR86t08/pL7K4xxIfy8ztTNKVtU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aL5gS39nMTeGqedqbJmczy0gSvftG7/jUKAHu7CnkfetJMpTrelWgktiChW2KM9qDNN0qK0WQ2G7nQFOznfn1vwnvr2E5VCgqt6uybddwNjNrhAOwR5ItS+5LVhp66WT3t2gEymY4zGO3frkFBigJQGsAeItBDLEMVcm1go2K8w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vVGcCEQR; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vVGcCEQR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 06E97C4CEF1; Tue, 16 Dec 2025 12:13:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1765887204; bh=yDiQO3+he43LRnEhUR86t08/pL7K4xxIfy8ztTNKVtU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vVGcCEQRIFcY22Qps5Z+nFSjEC08QELmLLPE4kuRctMP4lb9xMk1E8bVGuz27dxoB ww+uekUjWZnyJtV0w0S02Bzr7hNjQExxJh6tVOm3KS3F6XI6jsNikUE6l/ZPGPcyIu 4/wJDLSbDyRiCiOy9DW86lczhVBeVWiM8HuK+JOA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Arnd Bergmann , "Jason A. Donenfeld" , Sasha Levin Subject: [PATCH 6.18 158/614] random: use offstack cpumask when necessary Date: Tue, 16 Dec 2025 12:08:45 +0100 Message-ID: <20251216111407.060859596@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251216111401.280873349@linuxfoundation.org> References: <20251216111401.280873349@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: Arnd Bergmann [ Upstream commit 5d49f1a5bd358d24e5f88b23b46da833de1dbec8 ] The entropy generation function keeps a local cpu mask on the stack, which can trigger warnings in configurations with a large number of CPUs: drivers/char/random.c:1292:20: error: stack frame size (1288) exceeds limit (1280) in 'try_to_generate_entropy' [-Werror,-Wframe-larger-than] Use the cpumask interface to dynamically allocate it in those configurations. Fixes: 1c21fe00eda7 ("random: spread out jitter callback to different CPUs") Signed-off-by: Arnd Bergmann Signed-off-by: Jason A. Donenfeld Signed-off-by: Sasha Levin --- drivers/char/random.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index b8b24b6ed3fe4..4ba5f0c4c8b24 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1296,6 +1296,7 @@ static void __cold try_to_generate_entropy(void) struct entropy_timer_state *stack = PTR_ALIGN((void *)stack_bytes, SMP_CACHE_BYTES); unsigned int i, num_different = 0; unsigned long last = random_get_entropy(); + cpumask_var_t timer_cpus; int cpu = -1; for (i = 0; i < NUM_TRIAL_SAMPLES - 1; ++i) { @@ -1310,13 +1311,15 @@ static void __cold try_to_generate_entropy(void) atomic_set(&stack->samples, 0); timer_setup_on_stack(&stack->timer, entropy_timer, 0); + if (!alloc_cpumask_var(&timer_cpus, GFP_KERNEL)) + goto out; + while (!crng_ready() && !signal_pending(current)) { /* * Check !timer_pending() and then ensure that any previous callback has finished * executing by checking timer_delete_sync_try(), before queueing the next one. */ if (!timer_pending(&stack->timer) && timer_delete_sync_try(&stack->timer) >= 0) { - struct cpumask timer_cpus; unsigned int num_cpus; /* @@ -1326,19 +1329,19 @@ static void __cold try_to_generate_entropy(void) preempt_disable(); /* Only schedule callbacks on timer CPUs that are online. */ - cpumask_and(&timer_cpus, housekeeping_cpumask(HK_TYPE_TIMER), cpu_online_mask); - num_cpus = cpumask_weight(&timer_cpus); + cpumask_and(timer_cpus, housekeeping_cpumask(HK_TYPE_TIMER), cpu_online_mask); + num_cpus = cpumask_weight(timer_cpus); /* In very bizarre case of misconfiguration, fallback to all online. */ if (unlikely(num_cpus == 0)) { - timer_cpus = *cpu_online_mask; - num_cpus = cpumask_weight(&timer_cpus); + *timer_cpus = *cpu_online_mask; + num_cpus = cpumask_weight(timer_cpus); } /* Basic CPU round-robin, which avoids the current CPU. */ do { - cpu = cpumask_next(cpu, &timer_cpus); + cpu = cpumask_next(cpu, timer_cpus); if (cpu >= nr_cpu_ids) - cpu = cpumask_first(&timer_cpus); + cpu = cpumask_first(timer_cpus); } while (cpu == smp_processor_id() && num_cpus > 1); /* Expiring the timer at `jiffies` means it's the next tick. */ @@ -1354,6 +1357,8 @@ static void __cold try_to_generate_entropy(void) } mix_pool_bytes(&stack->entropy, sizeof(stack->entropy)); + free_cpumask_var(timer_cpus); +out: timer_delete_sync(&stack->timer); timer_destroy_on_stack(&stack->timer); } -- 2.51.0