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[84.135.184.41]) by smtp.gmail.com with ESMTPSA id x18sm9596308wmi.8.2021.02.11.03.58.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Feb 2021 03:58:47 -0800 (PST) Subject: Re: [PATCH] platform/surface: aggregator: Fix access of unaligned value To: Andy Shevchenko Cc: Hans de Goede , Mark Gross , platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-test-robot References: <20210210230411.1938660-1-luzmaximilian@gmail.com> From: Maximilian Luz Message-ID: Date: Thu, 11 Feb 2021 12:58:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: platform-driver-x86@vger.kernel.org On 2/11/21 11:22 AM, Andy Shevchenko wrote: > On Thu, Feb 11, 2021 at 12:04:11AM +0100, Maximilian Luz wrote: >> The raw message frame length is unaligned and explicitly marked as >> little endian. It should not be accessed without the appropriatte >> accessor functions. Fix this. > > Reviewed-by: Andy Shevchenko > Though a few nit-picks below. > >> Reported-by: kernel-test-robot >> Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem") >> Signed-off-by: Maximilian Luz >> --- >> drivers/platform/surface/aggregator/ssh_packet_layer.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.c b/drivers/platform/surface/aggregator/ssh_packet_layer.c >> index 583315db8b02..9a78188d8d1c 100644 >> --- a/drivers/platform/surface/aggregator/ssh_packet_layer.c >> +++ b/drivers/platform/surface/aggregator/ssh_packet_layer.c >> @@ -1774,7 +1774,8 @@ static size_t ssh_ptl_rx_eval(struct ssh_ptl *ptl, struct ssam_span *source) >> break; >> } >> >> - return aligned.ptr - source->ptr + SSH_MESSAGE_LENGTH(frame->len); >> + return aligned.ptr - source->ptr >> + + SSH_MESSAGE_LENGTH(get_unaligned_le16(&frame->len)); > > I would leave + on previous line. I can fix that if it bugs you. > Also it's possible to annotate temporary variable and use it, but it seems not > worth to do. Now that you mention it, we already have the correct frame length in payload.len. Let me draft up a new patch with that. > Side question: Do you think the below is correct (& operator)? > > sp.len = get_unaligned_le16(&((struct ssh_frame *)sf.ptr)->len); > > To me seems like you take an address to len member rather its value. That's the point though, no? The signature is u16 get_unaligned_le16(const void *p) so we do want a pointer to the len member. So I believe that is correct. > >> } >> >> static int ssh_ptl_rx_threadfn(void *data) >