Commit 661ea25e authored May 18, 2020 by Gustavo A. R. Silva Committed by Li Yang May 22, 2020

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://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21


[3] commit 76497732 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Qiang Zhao <qiang.zhao@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>

parent d3e81989

drivers/soc/fsl/qe/qe.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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++)
		/*

include/soc/fsl/qe/qe.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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));

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