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 894763BE54A; Tue, 16 Dec 2025 13:16:16 +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=1765890976; cv=none; b=R5kzp6DCO0G3Oim0Zt9gqSa6xLqz8iCSD5BY6/eCkvW+lwX1eU2M78Nemmsytnt5HBacVilUgJ/acG/q1DCb0f4qKjE/On4Jb1up4gyqjQcYRcVDwjjhKbMjNRayeQbelGf5CP71cjyeo/aJ3DD6f/mr+MOAAlQ8iAxbebEygPA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765890976; c=relaxed/simple; bh=2qLm7qLP78yIq98BOJp7Lpf5E6IukjXo8jHsSvSSKms=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ORh7yiyU/lwOZxtvg3dpzizeqNJbTqb84ggTklS2Q+Uq+3Np3+llrZl3oQHPyx49F0y8ysZyd9VyamChprbRncyFvt5XxE3IMBnBMciGjZmjFKBaZmsB5GqXuI4TmL85xwoOD1LaZ13YHxHwTQMCFR3AOhDbX9jAx9eKX6Y4lCo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=C31bi5xv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="C31bi5xv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBB61C4CEF1; Tue, 16 Dec 2025 13:16:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765890975; bh=2qLm7qLP78yIq98BOJp7Lpf5E6IukjXo8jHsSvSSKms=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=C31bi5xvG825o6nobsWDqZtAW94+2GEfq0tFJAY4/IUJ66prEIEsReaxEZpTyeHYd C3GI8SrEXQGf4QSar6YHgI7lSEdjzQR4w4bobdILk9cEXyn66yJaHasPTTWqBsUjYl d+U70VhhjCu3cbKzb+bNrbnVybzjglkIQYI/5wQqeoISeY5Op5vW6h8V+xWS2lNIv6 HGFowuDbT5FFgSRrJpu/6BTqhSPfq1gZotRgYZ1mFrAhSPcUOkxM2R+ey0S3/vJnoD H7FhB/XI9iPgVM6PHIl35evOYIay3hVAzKHRH0JiGrC0uji9msAiNMfYusWvZkRCQM KvFUhq4kBN3zw== Message-ID: <6d4b05af-40ec-4bbf-9045-f259315e5332@kernel.org> Date: Tue, 16 Dec 2025 14:16:11 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] w1: therm: Fix off-by-one buffer overflow in alarms_store To: David Laight Cc: Thorsten Blum , Huisong Li , Akira Shimahara , Greg Kroah-Hartman , stable@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251111204422.41993-2-thorsten.blum@linux.dev> <243ec26f-1fe1-4b3c-ab24-a6ebab163cde@kernel.org> <20251216092809.2e9b153d@pumpkin> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/12/2025 10:28, David Laight wrote: > On Tue, 16 Dec 2025 08:11:13 +0100 > Krzysztof Kozlowski wrote: > >> On 11/11/2025 21:44, Thorsten Blum wrote: >>> The sysfs buffer passed to alarms_store() is allocated with 'size + 1' >>> bytes and a NUL terminator is appended. However, the 'size' argument >>> does not account for this extra byte. The original code then allocated >>> 'size' bytes and used strcpy() to copy 'buf', which always writes one >>> byte past the allocated buffer since strcpy() copies until the NUL >>> terminator at index 'size'. >>> >>> Fix this by parsing the 'buf' parameter directly using simple_strtoll() >>> without allocating any intermediate memory or string copying. This >>> removes the overflow while simplifying the code. >>> >>> Cc: stable@vger.kernel.org >>> Fixes: e2c94d6f5720 ("w1_therm: adding alarm sysfs entry") >>> Signed-off-by: Thorsten Blum >>> --- >>> Compile-tested only. >>> >>> Changes in v4: >>> - Use simple_strtoll because kstrtoint also parses long long internally >>> - Return -ERANGE in addition to -EINVAL to match kstrtoint's behavior >>> - Remove any changes unrelated to fixing the buffer overflow (Krzysztof) >>> while maintaining the same behavior and return values as before >>> - Link to v3: https://lore.kernel.org/lkml/20251030155614.447905-1-thorsten.blum@linux.dev/ >>> >>> Changes in v3: >>> - Add integer range check for 'temp' to match kstrtoint() behavior >>> - Explicitly cast 'temp' to int when calling int_to_short() >>> - Link to v2: https://lore.kernel.org/lkml/20251029130045.70127-2-thorsten.blum@linux.dev/ >>> >>> Changes in v2: >>> - Fix buffer overflow instead of truncating the copy using strscpy() >>> - Parse buffer directly using simple_strtol() as suggested by David >>> - Update patch subject and description >>> - Link to v1: https://lore.kernel.org/lkml/20251017170047.114224-2-thorsten.blum@linux.dev/ >>> --- >>> drivers/w1/slaves/w1_therm.c | 64 ++++++++++++------------------------ >>> 1 file changed, 21 insertions(+), 43 deletions(-) >>> >>> diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c >>> index 9ccedb3264fb..5707fa34e804 100644 >>> --- a/drivers/w1/slaves/w1_therm.c >>> +++ b/drivers/w1/slaves/w1_therm.c >>> @@ -1836,55 +1836,36 @@ static ssize_t alarms_store(struct device *device, >>> struct w1_slave *sl = dev_to_w1_slave(device); >>> struct therm_info info; >>> u8 new_config_register[3]; /* array of data to be written */ >>> - int temp, ret; >>> - char *token = NULL; >>> + long long temp; >>> + int ret = 0; >>> s8 tl, th; /* 1 byte per value + temp ring order */ >>> - char *p_args, *orig; >>> - >>> - p_args = orig = kmalloc(size, GFP_KERNEL); >>> - /* Safe string copys as buf is const */ >>> - if (!p_args) { >>> - dev_warn(device, >>> - "%s: error unable to allocate memory %d\n", >>> - __func__, -ENOMEM); >>> - return size; >>> - } >>> - strcpy(p_args, buf); >>> - >>> - /* Split string using space char */ >>> - token = strsep(&p_args, " "); >>> - >>> - if (!token) { >>> - dev_info(device, >>> - "%s: error parsing args %d\n", __func__, -EINVAL); >>> - goto free_m; >>> - } >>> - >>> - /* Convert 1st entry to int */ >>> - ret = kstrtoint (token, 10, &temp); >>> + const char *p = buf; >>> + char *endp; >>> + >>> + temp = simple_strtoll(p, &endp, 10); >> >> Why using this, instead of explicitly encouraged kstrtoll()? > > Because the code needs to look at the terminating character. > The kstrtoxxx() family only support buffers that contain a single value. > While they return an indication of 'overflow' they are useless for > more general parameter parsing. > > The simple_strtoxxx() could detect overflow and then set 'endp' > to the digit that make the value too big - which should give an > error provided the callers checks the separator. Yes, there are two values here, so obviously this is right. Best regards, Krzysztof