[PATCH 0/2] Small fixes for qga

[PATCH 0/2] Small fixes for qga

[Daniel Xu]

These are two small fixes that fell out of [0]. Since we are not moving
forward with that patchset, I thought it would be good to at least send
the fixes that came out of it.

See commits for more details.

[0]: https://lore.kernel.org/qemu-devel/cover.1695034158.git.dxu@dxuuu.xyz/

Daniel Xu (2):
  qga: Fix memory leak when output stream is unused
  qapi: qga: Clarify when out-data and err-data are populated

 qga/commands.c       | 4 ++--
 qga/qapi-schema.json | 8 +++++---
 2 files changed, 7 insertions(+), 5 deletions(-)

-- 
2.42.0

[PATCH 1/2] qga: Fix memory leak when output stream is unused

[Daniel Xu]

If capture-output is requested but one of the channels goes unused (eg.
we attempt to capture stderr but the command never writes to stderr), we
can leak memory.

guest_exec_output_watch() is (from what I understand) unconditionally
called for both streams if output capture is requested. The first call
will always pass the `p->size == p->length` check b/c both values are
0. Then GUEST_EXEC_IO_SIZE bytes will be allocated for the stream.

But when we reap the exited process there's a `gei->err.length > 0`
check to actually free the buffer. Which does not get run if the command
doesn't write to the stream.

Fix by making free() unconditional.

Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
 qga/commands.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/qga/commands.c b/qga/commands.c
index 09c683e263..ce172edd2d 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -206,15 +206,15 @@ GuestExecStatus *qmp_guest_exec_status(int64_t pid, Error **errp)
 #endif
         if (gei->out.length > 0) {
             ges->out_data = g_base64_encode(gei->out.data, gei->out.length);
-            g_free(gei->out.data);
             ges->has_out_truncated = gei->out.truncated;
         }
+        g_free(gei->out.data);
 
         if (gei->err.length > 0) {
             ges->err_data = g_base64_encode(gei->err.data, gei->err.length);
-            g_free(gei->err.data);
             ges->has_err_truncated = gei->err.truncated;
         }
+        g_free(gei->err.data);
 
         QTAILQ_REMOVE(&guest_exec_state.processes, gei, next);
         g_free(gei);
-- 
2.42.0

[PATCH 2/2] qapi: qga: Clarify when out-data and err-data are populated

[Daniel Xu]

If output is being captured for a guest-exec invocation, the out-data
and err-data fields of guest-exec-status are only populated after the
process is reaped. This is somewhat counter intuitive and too late to
change. Thus, it would be good to document the behavior.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
 qga/qapi-schema.json | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index b720dd4379..876e2a8ea8 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -1220,11 +1220,13 @@
 # @signal: signal number (linux) or unhandled exception code (windows)
 #     if the process was abnormally terminated.
 #
-# @out-data: base64-encoded stdout of the process
+# @out-data: base64-encoded stdout of the process. This field will only
+#     be populated after the process exits.
 #
-# @err-data: base64-encoded stderr of the process Note: @out-data and
+# @err-data: base64-encoded stderr of the process. Note: @out-data and
 #     @err-data are present only if 'capture-output' was specified for
-#     'guest-exec'
+#     'guest-exec'. This field will only be populated after the process
+#     exits.
 #
 # @out-truncated: true if stdout was not fully captured due to size
 #     limitation.
-- 
2.42.0

Re: [PATCH 2/2] qapi: qga: Clarify when out-data and err-data are populated

[Konstantin Kostiuk]

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Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>

On Sun, Oct 1, 2023 at 9:39 PM Daniel Xu <dxu@dxuuu.xyz> wrote:

> If output is being captured for a guest-exec invocation, the out-data
> and err-data fields of guest-exec-status are only populated after the
> process is reaped. This is somewhat counter intuitive and too late to
> change. Thus, it would be good to document the behavior.
>
> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
> ---
>  qga/qapi-schema.json | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
> index b720dd4379..876e2a8ea8 100644
> --- a/qga/qapi-schema.json
> +++ b/qga/qapi-schema.json
> @@ -1220,11 +1220,13 @@
>  # @signal: signal number (linux) or unhandled exception code (windows)
>  #     if the process was abnormally terminated.
>  #
> -# @out-data: base64-encoded stdout of the process
> +# @out-data: base64-encoded stdout of the process. This field will only
> +#     be populated after the process exits.
>  #
> -# @err-data: base64-encoded stderr of the process Note: @out-data and
> +# @err-data: base64-encoded stderr of the process. Note: @out-data and
>  #     @err-data are present only if 'capture-output' was specified for
> -#     'guest-exec'
> +#     'guest-exec'. This field will only be populated after the process
> +#     exits.
>  #
>  # @out-truncated: true if stdout was not fully captured due to size
>  #     limitation.
> --
> 2.42.0
>
>

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Re: [PATCH 2/2] qapi: qga: Clarify when out-data and err-data are populated

[Markus Armbruster]

Daniel Xu <dxu@dxuuu.xyz> writes:

> If output is being captured for a guest-exec invocation, the out-data
> and err-data fields of guest-exec-status are only populated after the
> process is reaped. This is somewhat counter intuitive and too late to
> change. Thus, it would be good to document the behavior.
>
> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
> ---
>  qga/qapi-schema.json | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
> index b720dd4379..876e2a8ea8 100644
> --- a/qga/qapi-schema.json
> +++ b/qga/qapi-schema.json
> @@ -1220,11 +1220,13 @@
>  # @signal: signal number (linux) or unhandled exception code (windows)
>  #     if the process was abnormally terminated.
>  #
> -# @out-data: base64-encoded stdout of the process
> +# @out-data: base64-encoded stdout of the process. This field will only
> +#     be populated after the process exits.
>  #
> -# @err-data: base64-encoded stderr of the process Note: @out-data and
> +# @err-data: base64-encoded stderr of the process. Note: @out-data and
>  #     @err-data are present only if 'capture-output' was specified for
> -#     'guest-exec'
> +#     'guest-exec'. This field will only be populated after the process
> +#     exits.
>  #
>  # @out-truncated: true if stdout was not fully captured due to size
>  #     limitation.

Two spaces between sentences for consistency, please.

With that:
Acked-by: Markus Armbruster <armbru@redhat.com>

Re: [PATCH 0/2] Small fixes for qga

[Konstantin Kostiuk]

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merged

On Sun, Oct 1, 2023 at 9:39 PM Daniel Xu <dxu@dxuuu.xyz> wrote:

> These are two small fixes that fell out of [0]. Since we are not moving
> forward with that patchset, I thought it would be good to at least send
> the fixes that came out of it.
>
> See commits for more details.
>
> [0]:
> https://lore.kernel.org/qemu-devel/cover.1695034158.git.dxu@dxuuu.xyz/
>
> Daniel Xu (2):
>   qga: Fix memory leak when output stream is unused
>   qapi: qga: Clarify when out-data and err-data are populated
>
>  qga/commands.c       | 4 ++--
>  qga/qapi-schema.json | 8 +++++---
>  2 files changed, 7 insertions(+), 5 deletions(-)
>
> --
> 2.42.0
>
>

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