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R. Silva" To: Li Yang Subject: Re: [PATCH] soc: fsl: qe: Replace one-element array and use struct_size() helper Message-ID: <20200521000152.GC14138@embeddedor> References: <20200518221904.GA22274@embeddedor> <202005181529.C0CB448FBB@keescook> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200520_165704_419978_D6CED48F X-CRM114-Status: GOOD ( 33.93 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , "Gustavo A. R. Silva" , lkml , linuxppc-dev , "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" , Qiang Zhao Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 20, 2020 at 06:52:21PM -0500, Li Yang wrote: > On Mon, May 18, 2020 at 5:57 PM Kees Cook wrote: > > > > On Mon, May 18, 2020 at 05:19:04PM -0500, Gustavo A. R. Silva wrote: > > > The current codebase makes use of one-element arrays in the following > > > form: > > > > > > struct something { > > > int length; > > > u8 data[1]; > > > }; > > > > > > struct something *instance; > > > > > > instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL); > > > instance->length = size; > > > memcpy(instance->data, source, size); > > > > > > but the preferred mechanism to declare variable-length types such as > > > these ones is a flexible array member[1][2], introduced in C99: > > > > > > struct foo { > > > int stuff; > > > struct boo array[]; > > > }; > > > > > > By making use of the mechanism above, we will get a compiler warning > > > in case the flexible array does not occur last in the structure, which > > > will help us prevent some kind of undefined behavior bugs from being > > > inadvertently introduced[3] to the codebase from now on. So, replace > > > the one-element array with a flexible-array member. > > > > > > Also, make use of the new struct_size() helper to properly calculate the > > > size of struct qe_firmware. > > > > > > This issue was found with the help of Coccinelle and, audited and fixed > > > _manually_. > > > > > > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html > > > [2] https://github.com/KSPP/linux/issues/21 > > > [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") > > > > > > Signed-off-by: Gustavo A. R. Silva > > > --- > > > drivers/soc/fsl/qe/qe.c | 4 ++-- > > > include/soc/fsl/qe/qe.h | 2 +- > > > 2 files changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/soc/fsl/qe/qe.c b/drivers/soc/fsl/qe/qe.c > > > index 447146861c2c1..2df20d6f85fa4 100644 > > > --- a/drivers/soc/fsl/qe/qe.c > > > +++ b/drivers/soc/fsl/qe/qe.c > > > @@ -448,7 +448,7 @@ int qe_upload_firmware(const struct qe_firmware *firmware) > > > unsigned int i; > > > unsigned int j; > > > u32 crc; > > > - size_t calc_size = sizeof(struct qe_firmware); > > > + size_t calc_size; > > > size_t length; > > > const struct qe_header *hdr; > > > > > > @@ -480,7 +480,7 @@ int qe_upload_firmware(const struct qe_firmware *firmware) > > > } > > > > > > /* Validate the length and check if there's a CRC */ > > > - calc_size += (firmware->count - 1) * sizeof(struct qe_microcode); > > > + calc_size = struct_size(firmware, microcode, firmware->count); > > > > > > for (i = 0; i < firmware->count; i++) > > > /* > > > diff --git a/include/soc/fsl/qe/qe.h b/include/soc/fsl/qe/qe.h > > > index e282ac01ec081..3feddfec9f87d 100644 > > > --- a/include/soc/fsl/qe/qe.h > > > +++ b/include/soc/fsl/qe/qe.h > > > @@ -307,7 +307,7 @@ struct qe_firmware { > > > u8 revision; /* The microcode version revision */ > > > u8 padding; /* Reserved, for alignment */ > > > u8 reserved[4]; /* Reserved, for future expansion */ > > > - } __attribute__ ((packed)) microcode[1]; > > > + } __packed microcode[]; > > > /* All microcode binaries should be located here */ > > > /* CRC32 should be located here, after the microcode binaries */ > > > } __attribute__ ((packed)); > > > -- > > > 2.26.2 > > > > > > > Hm, looking at this code, I see a few other things that need to be > > fixed: > > > > 1) drivers/tty/serial/ucc_uart.c does not do a be32_to_cpu() conversion > > on the length test (understandably, a little-endian system has never run > > this code since it's ppc specific), but it's still wrong: > > > > if (firmware->header.length != fw->size) { > > > > compare to the firmware loader: > > > > length = be32_to_cpu(hdr->length); > > > > 2) drivers/soc/fsl/qe/qe.c does not perform bounds checking on the > > per-microcode offsets, so the uploader might send data outside the > > firmware buffer. Perhaps: > > We do validate the CRC for each microcode, it is unlikely the CRC > check can pass if the offset or length is not correct. But you are > probably right that it will be safer to check the boundary and fail > quicker before we actually start the CRC check. Will you come up with > a formal patch or you want us to deal with it? > Li, I will send a proper patch for this. Thanks -- Gustavo > > > > > > diff --git a/drivers/soc/fsl/qe/qe.c b/drivers/soc/fsl/qe/qe.c > > index 447146861c2c..c4e0bc452f03 100644 > > --- a/drivers/soc/fsl/qe/qe.c > > +++ b/drivers/soc/fsl/qe/qe.c > > @@ -451,6 +451,7 @@ int qe_upload_firmware(const struct qe_firmware *firmware) > > size_t calc_size = sizeof(struct qe_firmware); > > size_t length; > > const struct qe_header *hdr; > > + void *firmware_end; > > > > if (!firmware) { > > printk(KERN_ERR "qe-firmware: invalid pointer\n"); > > @@ -491,19 +492,39 @@ int qe_upload_firmware(const struct qe_firmware *firmware) > > calc_size += sizeof(__be32) * > > be32_to_cpu(firmware->microcode[i].count); > > > > - /* Validate the length */ > > + /* Validate total length */ > > if (length != calc_size + sizeof(__be32)) { > > printk(KERN_ERR "qe-firmware: invalid length\n"); > > return -EPERM; > > } > > > > /* Validate the CRC */ > > - crc = be32_to_cpu(*(__be32 *)((void *)firmware + calc_size)); > > + firmware_end = (void *)firmware + calc_size; > > + crc = be32_to_cpu(*(__be32 *)firmware_end); > > if (crc != crc32(0, firmware, calc_size)) { > > printk(KERN_ERR "qe-firmware: firmware CRC is invalid\n"); > > return -EIO; > > } > > > > + /* Validate ucode lengths and offsets */ > > + for (i = 0; i < firmware->count; i++) { > > + const struct qe_microcode *ucode = &firmware->microcode[i]; > > + __be32 *code; > > + size_t count; > > + > > + if (!ucode->code_offset) > > + continue; > > + > > + code = (void *)firmware + be32_to_cpu(ucode->code_offset); > > + count = be32_to_cpu(ucode->count) * sizeof(*code); > > + > > + if (code < firmware || code >= firmware_end || > > + code + count < firmware || code + count >= firmware_end) { > > + printk(KERN_ERR "qe-firmware: invalid ucode offset\n"); > > + return -EIO; > > + } > > + } > > + > > /* > > * If the microcode calls for it, split the I-RAM. > > */ > > > > > > I haven't tested this. > > > > > > -- > > Kees Cook _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel