[PATCH] util/error: Fix use-after-free errors reported by Coverity

[PATCH] util/error: Fix use-after-free errors reported by Coverity

[Stefan Berger]

Fix use-after-free errors in the code path that called error_handle(). A
call to error_handle() will now either free the passed Error 'err' or
assign it to '*errp' if '*errp' is currently NULL. This ensures that 'err'
either has been freed or is assigned to '*errp' if this function returns.
Adjust the two callers of this function to not assign the 'err' to '*errp'
themselves, since this is now handled by error_handle().

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 util/error.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/util/error.c b/util/error.c
index 5537245da6..e5e247209a 100644
--- a/util/error.c
+++ b/util/error.c
@@ -46,6 +46,10 @@ static void error_handle(Error **errp, Error *err)
     }
     if (errp == &error_warn) {
         warn_report_err(err);
+    } else if (errp && !*errp) {
+        *errp = err;
+    } else {
+        error_free(err);
     }
 }
 
@@ -76,7 +80,6 @@ static void error_setv(Error **errp,
     err->func = func;
 
     error_handle(errp, err);
-    *errp = err;
 
     errno = saved_errno;
 }
@@ -289,11 +292,6 @@ void error_propagate(Error **dst_errp, Error *local_err)
         return;
     }
     error_handle(dst_errp, local_err);
-    if (dst_errp && !*dst_errp) {
-        *dst_errp = local_err;
-    } else {
-        error_free(local_err);
-    }
 }
 
 void error_propagate_prepend(Error **dst_errp, Error *err,
-- 
2.39.1

Re: [PATCH] util/error: Fix use-after-free errors reported by Coverity

[Peter Maydell]

On Thu, 6 Apr 2023 at 16:43, Stefan Berger <stefanb@linux.ibm.com> wrote:
>
> Fix use-after-free errors in the code path that called error_handle(). A
> call to error_handle() will now either free the passed Error 'err' or
> assign it to '*errp' if '*errp' is currently NULL. This ensures that 'err'
> either has been freed or is assigned to '*errp' if this function returns.
> Adjust the two callers of this function to not assign the 'err' to '*errp'
> themselves, since this is now handled by error_handle().
>
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> ---

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

Do we think this needs to be fixed for 8.0 ?

thanks
-- PMM

Re: [PATCH] util/error: Fix use-after-free errors reported by Coverity

[Philippe Mathieu-Daudé]

On 6/4/23 17:43, Stefan Berger wrote:
> Fix use-after-free errors in the code path that called error_handle(). A
> call to error_handle() will now either free the passed Error 'err' or
> assign it to '*errp' if '*errp' is currently NULL. This ensures that 'err'
> either has been freed or is assigned to '*errp' if this function returns.
> Adjust the two callers of this function to not assign the 'err' to '*errp'
> themselves, since this is now handled by error_handle().
> 
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
>   util/error.c | 10 ++++------
>   1 file changed, 4 insertions(+), 6 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH] util/error: Fix use-after-free errors reported by Coverity

[Marc-André Lureau]

Hi

On Thu, Apr 6, 2023 at 7:43 PM Stefan Berger <stefanb@linux.ibm.com> wrote:
>
> Fix use-after-free errors in the code path that called error_handle(). A
> call to error_handle() will now either free the passed Error 'err' or
> assign it to '*errp' if '*errp' is currently NULL. This ensures that 'err'
> either has been freed or is assigned to '*errp' if this function returns.
> Adjust the two callers of this function to not assign the 'err' to '*errp'
> themselves, since this is now handled by error_handle().
>

Fixes: commit 3ffef1a55ca3 ("error: add global &error_warn destination")

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

worth including for 8.0 imho.

> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
>  util/error.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/util/error.c b/util/error.c
> index 5537245da6..e5e247209a 100644
> --- a/util/error.c
> +++ b/util/error.c
> @@ -46,6 +46,10 @@ static void error_handle(Error **errp, Error *err)
>      }
>      if (errp == &error_warn) {
>          warn_report_err(err);
> +    } else if (errp && !*errp) {
> +        *errp = err;
> +    } else {
> +        error_free(err);
>      }
>  }
>
> @@ -76,7 +80,6 @@ static void error_setv(Error **errp,
>      err->func = func;
>
>      error_handle(errp, err);
> -    *errp = err;
>
>      errno = saved_errno;
>  }
> @@ -289,11 +292,6 @@ void error_propagate(Error **dst_errp, Error *local_err)
>          return;
>      }
>      error_handle(dst_errp, local_err);
> -    if (dst_errp && !*dst_errp) {
> -        *dst_errp = local_err;
> -    } else {
> -        error_free(local_err);
> -    }
>  }
>
>  void error_propagate_prepend(Error **dst_errp, Error *err,
> --
> 2.39.1
>


-- 
Marc-André Lureau