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 D5CC869942; Wed, 21 Feb 2024 14:17:11 +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=1708525031; cv=none; b=V0qdpCOIDbMblFoJ/DyNVthVeLESBOiKPP0ls5PG1h/N9Z75KabygjW5LKq/i+ngon/LOWx22Q1yeKv54wMeF/jVSoAzY/9b/HV/Sd5maoWH0Pnzw3tQZ6479PIhN4k04TYPQTiMXEdbSKdcKVyIHRHGv7T9Qicf4cjMdKDkluY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708525031; c=relaxed/simple; bh=Nnza780wQQTXhac5HhLFwlQvfolKUt7QOp/b2BHAQu0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NJjRUYZWtF7T06Sgrtr5AQg1AKvxcbeKzWnaTCjx15giEBX+VFqskkC1SZTrAVOPwFSc64Qd/ez6AiYwAAm3m1QRu5XcK2/mJRVHjOlmClM+e+UZPhQAxv0lDeKQvhSHistZVnzIx2A5HCXNI8tWeGhc19UiRsuHsRw6HtMimiM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=yXxFGC8Z; 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="yXxFGC8Z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC746C433C7; Wed, 21 Feb 2024 14:17:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708525031; bh=Nnza780wQQTXhac5HhLFwlQvfolKUt7QOp/b2BHAQu0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yXxFGC8ZK8ZO3l5JyUiCj6C8B9ITOsPzaRYnzqCa7jcrsPUBw52L947pDT6vvPHe/ 1NJdBSzVn7459i7ft0C5cBSkk9fjk23nOASiPH7RKRvcU1azWuqDFoZIQhTz7n1DVE rPVDS5EyEx3AfymV41c+1EwhQIAJgUqeldRO+J8Q= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Edward Adam Davis , syzbot+c52ab18308964d248092@syzkaller.appspotmail.com, Herbert Xu Subject: [PATCH 5.4 012/267] hwrng: core - Fix page fault dead lock on mmap-ed hwrng Date: Wed, 21 Feb 2024 14:05:53 +0100 Message-ID: <20240221125940.443783840@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240221125940.058369148@linuxfoundation.org> References: <20240221125940.058369148@linuxfoundation.org> User-Agent: quilt/0.67 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 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Herbert Xu commit 78aafb3884f6bc6636efcc1760c891c8500b9922 upstream. There is a dead-lock in the hwrng device read path. This triggers when the user reads from /dev/hwrng into memory also mmap-ed from /dev/hwrng. The resulting page fault triggers a recursive read which then dead-locks. Fix this by using a stack buffer when calling copy_to_user. Reported-by: Edward Adam Davis Reported-by: syzbot+c52ab18308964d248092@syzkaller.appspotmail.com Fixes: 9996508b3353 ("hwrng: core - Replace u32 in driver API with byte array") Cc: Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- drivers/char/hw_random/core.c | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-) --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -24,10 +24,13 @@ #include #include #include +#include #include #define RNG_MODULE_NAME "hw_random" +#define RNG_BUFFER_SIZE (SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES) + static struct hwrng *current_rng; /* the current rng has been explicitly chosen by user via sysfs */ static int cur_rng_set_by_user; @@ -59,7 +62,7 @@ static inline int rng_get_data(struct hw static size_t rng_buffer_size(void) { - return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES; + return RNG_BUFFER_SIZE; } static void add_early_randomness(struct hwrng *rng) @@ -202,6 +205,7 @@ static inline int rng_get_data(struct hw static ssize_t rng_dev_read(struct file *filp, char __user *buf, size_t size, loff_t *offp) { + u8 buffer[RNG_BUFFER_SIZE]; ssize_t ret = 0; int err = 0; int bytes_read, len; @@ -229,34 +233,37 @@ static ssize_t rng_dev_read(struct file if (bytes_read < 0) { err = bytes_read; goto out_unlock_reading; + } else if (bytes_read == 0 && + (filp->f_flags & O_NONBLOCK)) { + err = -EAGAIN; + goto out_unlock_reading; } + data_avail = bytes_read; } - if (!data_avail) { - if (filp->f_flags & O_NONBLOCK) { - err = -EAGAIN; - goto out_unlock_reading; - } - } else { - len = data_avail; + len = data_avail; + if (len) { if (len > size) len = size; data_avail -= len; - if (copy_to_user(buf + ret, rng_buffer + data_avail, - len)) { + memcpy(buffer, rng_buffer + data_avail, len); + } + mutex_unlock(&reading_mutex); + put_rng(rng); + + if (len) { + if (copy_to_user(buf + ret, buffer, len)) { err = -EFAULT; - goto out_unlock_reading; + goto out; } size -= len; ret += len; } - mutex_unlock(&reading_mutex); - put_rng(rng); if (need_resched()) schedule_timeout_interruptible(1); @@ -267,6 +274,7 @@ static ssize_t rng_dev_read(struct file } } out: + memzero_explicit(buffer, sizeof(buffer)); return ret ? : err; out_unlock_reading: