Re: [PATCH v2] drivers/firmware/broadcom/bcm47xx_nvram.c: fix incorrect __ioread32_copy

Hauke Mehrtens
2016-03-23T21:44:08Z

On 03/16/2016 12:06 AM, Aaro Koskinen wrote:
> Commit 1f330c327900 ("drivers/firmware/broadcom/bcm47xx_nvram.c: use
> __ioread32_copy() instead of open-coding") switched to use a generic copy
> function, but failed to notice that the header pointer is updated between
> the two copies, resulting in bogus data being copied in the latter one.
> Fix by keeping the old header pointer.
>
> The patch fixes totally broken networking on WRT54GL router (both LAN
> and WLAN interfaces fail to probe).
>
> Fixes: 1f330c327900 ("drivers/firmware/broadcom/bcm47xx_nvram.c: use __ioread32_copy() instead of open-coding")
> Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> ---
>
> v2: Avoid using the device memory after the first copy when
> checking the nvram length, suggested by Stephen Boyd.
>
> v1: http://marc.info/?t=145807850800003&r=1&w=2
>
> drivers/firmware/broadcom/bcm47xx_nvram.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/firmware/broadcom/bcm47xx_nvram.c b/drivers/firmware/broadcom/bcm47xx_nvram.c
> index 0c2f0a6..0b631e5 100644
> --- a/drivers/firmware/broadcom/bcm47xx_nvram.c
> +++ b/drivers/firmware/broadcom/bcm47xx_nvram.c
> @@ -94,15 +94,14 @@ static int nvram_find_and_copy(void __iomem *iobase, u32 lim)
>
> found:
> __ioread32_copy(nvram_buf, header, sizeof(*header) / 4);
> - header = (struct nvram_header *)nvram_buf;
> - nvram_len = header->len;
> + nvram_len = ((struct nvram_header *)(nvram_buf))->len;

I do not understand why this change is needed? Doesn't the old code do
exactly the same as the new one?

The old code updated the header pointer and then accesses a member, the
new one directly accesses this member without updating this pointer.

I assume, I am missing something. ;-)

> if (nvram_len > size) {
> pr_err("The nvram size according to the header seems to be bigger than the partition on flash\n");
> nvram_len = size;
> }
> if (nvram_len >= NVRAM_SPACE) {
> pr_err("nvram on flash (%i bytes) is bigger than the reserved space in memory, will just copy the first %i bytes\n",
> - header->len, NVRAM_SPACE - 1);
> + nvram_len, NVRAM_SPACE - 1);
> nvram_len = NVRAM_SPACE - 1;
> }
> /* proceed reading data after header */
>