Valgrind complains about the probe_o_direct_support() function reading
from an uninitialized buffer. For probing O_DIRECT support we don't
actually need to write to the file, just make sure the pwrite call
doesn't reject the write. Still, write zeroes to the buffer to
suppress the warning.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 tests/qtest/migration-helpers.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tests/qtest/migration-helpers.c b/tests/qtest/migration-helpers.c
index 3f8ba7fa8e..981910ba35 100644
--- a/tests/qtest/migration-helpers.c
+++ b/tests/qtest/migration-helpers.c
@@ -496,6 +496,7 @@ bool probe_o_direct_support(const char *tmpfs)
 
     buf = qemu_try_memalign(len, len);
     g_assert(buf);
+    memset(buf, 0, len);
 
     ret = pwrite(fd, buf, len, offset);
     unlink(filename);
-- 
2.35.3

On Mon, Dec 09, 2024 at 05:44:23PM -0300, Fabiano Rosas wrote:
> Valgrind complains about the probe_o_direct_support() function reading
> from an uninitialized buffer. For probing O_DIRECT support we don't
> actually need to write to the file, just make sure the pwrite call
> doesn't reject the write. Still, write zeroes to the buffer to
> suppress the warning.
> 
> Signed-off-by: Fabiano Rosas <farosas@suse.de>

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu

On 9/12/24 21:44, Fabiano Rosas wrote:
> Valgrind complains about the probe_o_direct_support() function reading
> from an uninitialized buffer. For probing O_DIRECT support we don't
> actually need to write to the file, just make sure the pwrite call
> doesn't reject the write. Still, write zeroes to the buffer to
> suppress the warning.
> 
> Signed-off-by: Fabiano Rosas <farosas@suse.de>
> ---
>   tests/qtest/migration-helpers.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/tests/qtest/migration-helpers.c b/tests/qtest/migration-helpers.c
> index 3f8ba7fa8e..981910ba35 100644
> --- a/tests/qtest/migration-helpers.c
> +++ b/tests/qtest/migration-helpers.c
> @@ -496,6 +496,7 @@ bool probe_o_direct_support(const char *tmpfs)
>   
>       buf = qemu_try_memalign(len, len);
>       g_assert(buf);

(we could directly use qemu_memalign here)

> +    memset(buf, 0, len);
>   
>       ret = pwrite(fd, buf, len, offset);
>       unlink(filename);

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