On Sat, Feb 14, 2015 at 9:34 PM, Tobias Stoeckmann
<tobias@xxxxxxxxxxxxxx> wrote:
> Hi,
>
> a segmentation fault occurs if a module has an empty key attached to
> its signature.
>
> This happens because it's assumed that at least one key byte is
> available, subtracting it in libkmod-module line 2249. This -1 value
> is casted to an unsigned data type later on, resulting in illegal
> memory access.
>
> Attached please find a proof of concept module, tested on amd64:
>
> tobias:~$ modinfo 0sig.ko
> filename: /home/tobias/0sig.ko
> Segmentation fault
>
> Tobias
> ---
> libkmod/libkmod-module.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
> index 30f15ca..ca703a7 100644
> --- a/libkmod/libkmod-module.c
> +++ b/libkmod/libkmod-module.c
> @@ -2246,7 +2246,8 @@ KMOD_EXPORT int kmod_module_get_info(const struct kmod_module *mod, struct kmod_
> key_hex[i * 3 + 2] = ':';
> }
> n = kmod_module_info_append(list, "sig_key", strlen("sig_key"),
> - key_hex, sig_info.key_id_len * 3 - 1);
> + key_hex, sig_info.key_id_len == 0 ? 0 :
> + sig_info.key_id_len * 3 - 1);
This one I prefer changing kmod_module_signature_info() to do the
right thing. This is because a 0 len signature is not a valid
signature and I prefer outputting nothing in modinfo rather than a
bogus signature.
Just pushed a commit changing kmod_module_signature_info(). Please
take a look if it fixes your issue.
thanks
--
Lucas De Marchi
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