On Wed, Jun 23, 2021 at 08:00:21PM +0200, Philippe Mathieu-Daudé wrote:
> In commit a9bcedd15a5 ("hw/sd/sdcard: Do not allow invalid SD card
> sizes") we tried to protect us from CVE-2020-13253 by only allowing
> card with power-of-2 sizes. However doing so we disrupted valid user
> cases. As a compromise, allow any card size, but warn only power of 2
> sizes are supported, still suggesting the user how to increase a
> card with 'qemu-img resize'.
>
> Cc: Tom Yan <[email protected]>
> Cc: Warner Losh <[email protected]>
> Buglink: https://bugs.launchpad.net/qemu/+bug/1910586
> Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
> ---
> hw/sd/sd.c | 25 +++++++++----------------
> 1 file changed, 9 insertions(+), 16 deletions(-)
>
> diff --git a/hw/sd/sd.c b/hw/sd/sd.c
> index 9c8dd11bad1..cab4aab1475 100644
> --- a/hw/sd/sd.c
> +++ b/hw/sd/sd.c
> @@ -2131,23 +2131,16 @@ static void sd_realize(DeviceState *dev, Error **errp)
> blk_size = blk_getlength(sd->blk);
> if (blk_size > 0 && !is_power_of_2(blk_size)) {
> int64_t blk_size_aligned = pow2ceil(blk_size);
> - char *blk_size_str;
> + g_autofree char *blk_size_s = size_to_str(blk_size);
> + g_autofree char *blk_size_aligned_s =
> size_to_str(blk_size_aligned);
>
> - blk_size_str = size_to_str(blk_size);
> - error_setg(errp, "Invalid SD card size: %s", blk_size_str);
> - g_free(blk_size_str);
> -
> - blk_size_str = size_to_str(blk_size_aligned);
> - error_append_hint(errp,
> - "SD card size has to be a power of 2, e.g.
> %s.\n"
> - "You can resize disk images with"
> - " 'qemu-img resize <imagefile> <new-size>'\n"
> - "(note that this will lose data if you make
> the"
> - " image smaller than it currently is).\n",
> - blk_size_str);
> - g_free(blk_size_str);
> -
> - return;
> + warn_report("SD card size is not a power of 2 (%s). It might
> work"
> + " but is not supported by QEMU. If possible, resize"
> + " your disk image to %s with:",
> + blk_size_s, blk_size_aligned_s);
> + warn_report(" 'qemu-img resize <imagefile> <new-size>'");
> + warn_report("(note that this will lose data if you make the"
> + " image smaller than it currently is).");
In what scenarios will non-power of 2 not work and what is the effect ?
Is it a QEMU bug or not ?
Regards,
Daniel
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