Re: [Qemu-devel] [PATCH] coverity-model: replay data is considered trusted

[Markus Armbruster]

Paolo Bonzini <address@hidden> writes:

> Replay data is not considered a possible attack vector; add a model that
> does not use getc so that "tainted data" warnings are suppressed.
>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  scripts/coverity-model.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/scripts/coverity-model.c b/scripts/coverity-model.c
> index c702804f41..576f48de33 100644
> --- a/scripts/coverity-model.c
> +++ b/scripts/coverity-model.c
> @@ -103,6 +103,19 @@ static int get_keysym(const name2keysym_t *table,
>      }
>  }
>  
> +
> +/* Replay data is considered trusted.  */
> +uint8_t replay_get_byte(void)
> +{
> +     uint8_t byte = 0;
> +     if (replay_file) {
> +         uint8_t c;
> +         byte = c;
> +     }
> +     return byte;
> +}
> +
> +
>  /*
>   * GLib memory allocation functions.
>   *

Coverity 2018.06 chokes on this:

    $ cov-make-library -of scripts/coverity-model.xmldb 
scripts/coverity-model.c 
    output file: scripts/coverity-model.xmldb
    Compiling scripts/coverity-model.c with command 
/opt/cov-sa-2018.06/bin/cov-emit --dir 
/tmp/cov-armbru/930a6fb31e5f464fc1a53354b2deb66b/cov-make-library-emit -w 
--no_error_recovery --emit_header_functions --no_implicit_decl --preinclude 
/opt/cov-sa-2018.06/library/decls.h --c scripts/coverity-model.c
    "scripts/coverity-model.c", line 110: error #20: identifier "replay_file" is
              undefined
           if (replay_file) {
               ^

    Emit for file '/work/armbru/qemu/scripts/coverity-model.c' complete.
    [ERROR] 1 error detected in the compilation of "scripts/coverity-model.c".
    ERROR: cov-emit returned with code 1

Minimal fix:

    diff --git a/scripts/coverity-model.c b/scripts/coverity-model.c
    index 48b112393b..f987ce53b8 100644
    --- a/scripts/coverity-model.c
    +++ b/scripts/coverity-model.c
    @@ -106,6 +106,7 @@ static int get_keysym(const name2keysym_t *table,
     /* Replay data is considered trusted.  */
     uint8_t replay_get_byte(void)
     {
    +    void *replay_file;
          uint8_t byte = 0;
          if (replay_file) {
              uint8_t c;

Alternatively, dumb down to:

    /* Replay data is considered trusted.  */
    uint8_t replay_get_byte(void)
    {
        uint8_t byte;
        return byte;
    }

Got a preference?