-----Original Message-----
From: Gustavo A. R. Silva <gustavoars@kernel.org>
Sent: 2020年5月19日 6:19
To: Qiang Zhao <qiang.zhao@nxp.com>; Leo Li <redacted>
Cc: linuxppc-dev@lists.ozlabs.org; linux-arm-kernel@lists.infradead.org;
linux-kernel@vger.kernel.org; Gustavo A. R. Silva [off-list ref];
Kees Cook [off-list ref]
Subject: [PATCH] soc: fsl: qe: Replace one-element array and use struct_size()
helper

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://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.
org%2Fonlinedocs%2Fgcc%2FZero-Length.html&amp;data=02%7C01%7Cqiang.
zhao%40nxp.com%7Cb058bcb9af134df8446808d7fb78cfa9%7C686ea1d3bc2b
4c6fa92cd99c5c301635%7C0%7C0%7C637254368610203908&amp;sdata=70
a6VBg3oWQf9a5KICuCEuIj6gw57NKYhNv2JL8JdDY%3D&amp;reserved=0
[2]
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.c
om%2FKSPP%2Flinux%2Fissues%2F21&amp;data=02%7C01%7Cqiang.zhao%40
nxp.com%7Cb058bcb9af134df8446808d7fb78cfa9%7C686ea1d3bc2b4c6fa92c
d99c5c301635%7C0%7C0%7C637254368610213901&amp;sdata=kVyNBYHbm
a5jCO9pbkoHMetHEYGvWDq6Xw%2BBeC7uHII%3D&amp;reserved=0
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 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