Re: [Qemu-devel] [PATCH 1/3] i386: fix regression parsing multiboot initrd modules

[Peter Maydell]

On 14 May 2018 at 18:19, Daniel P. Berrangé <address@hidden> wrote:
> The logic for parsing the multiboot initrd modules was messed up in
>
>   commit 950c4e6c94b15cd0d8b63891dddd7a8dbf458e6a
>   Author: Daniel P. Berrangé <address@hidden>
>   Date:   Mon Apr 16 12:17:43 2018 +0100
>
>     opts: don't silently truncate long option values
>
> Causing the length to be undercounter, and the number of modules over
> counted. It also passes NULL to get_opt_value() which was not robust
> at accepting a NULL value.
>
> Signed-off-by: Daniel P. Berrangé <address@hidden>
> ---
>  hw/i386/multiboot.c | 3 +--
>  util/qemu-option.c  | 4 +++-
>  2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
> index 7a2953e26f..8e26545814 100644
> --- a/hw/i386/multiboot.c
> +++ b/hw/i386/multiboot.c
> @@ -292,8 +292,7 @@ int load_multiboot(FWCfgState *fw_cfg,
>      cmdline_len += strlen(kernel_cmdline) + 1;
>      if (initrd_filename) {
>          const char *r = get_opt_value(initrd_filename, NULL);
> -        cmdline_len += strlen(r) + 1;
> -        mbs.mb_mods_avail = 1;
> +        cmdline_len += strlen(initrd_filename) + 1;
>          while (1) {
>              mbs.mb_mods_avail++;
>              r = get_opt_value(r, NULL);
> diff --git a/util/qemu-option.c b/util/qemu-option.c
> index 58d1c23893..8a68bc2314 100644
> --- a/util/qemu-option.c
> +++ b/util/qemu-option.c
> @@ -75,7 +75,9 @@ const char *get_opt_value(const char *p, char **value)
>      size_t capacity = 0, length;
>      const char *offset;
>
> -    *value = NULL;
> +    if (value) {
> +        *value = NULL;
> +    }
>      while (1) {
>          offset = strchr(p, ',');
>          if (!offset) {

Don't we delete this check again in patch 3? If we're
going to fix this by making multiboot.c not pass in NULL pointers,
is there a reason not to simply do that?

thanks
-- PMM