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Fri, 14 Nov 2025 05:39:58 -0800 (PST) MIME-Version: 1.0 References: <20251106072818.25075-1-zhaoguohan_salmon@163.com> In-Reply-To: <20251106072818.25075-1-zhaoguohan_salmon@163.com> From: Peter Maydell Date: Fri, 14 Nov 2025 13:39:46 +0000 X-Gm-Features: AWmQ_bnibtEUyNBGrExc6YBi2sUcAlbg0xcPORXfpM1jRDgeULh0lupb7314kC0 Message-ID: Subject: Re: [PATCH] hw/sd/sdcard: fix potential out-of-bounds read in rpmb_calc_hmac To: zhaoguohan_salmon@163.com Cc: philmd@linaro.org, bmeng.cn@gmail.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, GuoHan Zhao , Jan Kiszka Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2607:f8b0:4864:20::b132; envelope-from=peter.maydell@linaro.org; helo=mail-yx1-xb132.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, 6 Nov 2025 at 07:29, wrote: > > From: GuoHan Zhao > > Coverity reported a potential out-of-bounds read in rpmb_calc_hmac(): > > CID 1642869: Out-of-bounds read (OVERRUN) > Overrunning array of 256 bytes at byte offset 256 by dereferencing > pointer &frame->data[256]. > > The issue arises from using &frame->data[RPMB_DATA_LEN] as the source > pointer for memcpy(). Although computing a one-past-the-end pointer is > legal, dereferencing it (as memcpy() does) is undefined behavior in C. > > Signed-off-by: GuoHan Zhao > --- > hw/sd/sd.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/hw/sd/sd.c b/hw/sd/sd.c > index 9c86c016cc9d..bc2e9863a534 100644 > --- a/hw/sd/sd.c > +++ b/hw/sd/sd.c > @@ -1161,7 +1161,8 @@ static bool rpmb_calc_hmac(SDState *sd, const RPMBDataFrame *frame, > > assert(RPMB_HASH_LEN <= sizeof(sd->data)); > > - memcpy((uint8_t *)buf + RPMB_DATA_LEN, &frame->data[RPMB_DATA_LEN], > + memcpy((uint8_t *)buf + RPMB_DATA_LEN, > + (const uint8_t *)frame + RPMB_DATA_LEN, > RPMB_HASH_LEN - RPMB_DATA_LEN); > offset = lduw_be_p(&frame->address) * RPMB_DATA_LEN + sd_part_offset(sd); > do { What is this code even trying to do ? We define a RPMBDataFrame which is a packed struct, but now we're randomly memcpying a lump of data out of the middle of it ?? The start of the struct is uint8_t stuff_bytes[RPMB_STUFF_LEN]; // offset 0 uint8_t key_mac[RPMB_KEY_MAC_LEN]; // offset 196 uint8_t data[RPMB_DATA_LEN]; // offset 228 uint8_t nonce[RPMB_NONCE_LEN]; // offset 484 so frame + RPMB_DATA_LEN (256) starts 28 bytes into the data array; and then we're copying 28 bytes of data? The existing code (frame->data[RPMB_DATA_LEN]) doesn't make sense either, as that's a weird way to write frame->nonce, and the RPMB_NONCE_LEN doesn't have the same length as what we're copying either. Can somebody who understands this explain what this code is intended to be doing ? thanks -- PMM