[PATCH 02/12] drm/panic: Make allocation of zlib workspace more robust

[Thomas Zimmermann <tzimmermann@suse.de>]

Test the zlib workspace size to not have a negative value. This
would be a driver bug. Also touch allocated memory so that the
pages are available upon a panic.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_panic.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
index 0685f7d8dba2..705b72bf0d83 100644
--- a/drivers/gpu/drm/drm_panic.c
+++ b/drivers/gpu/drm/drm_panic.c
@@ -634,13 +634,19 @@ static struct z_stream_s stream;
 
 static void __init drm_panic_qr_init(void)
 {
+	int wssize;
+
+	wssize = zlib_deflate_workspacesize(WINDOW_BITS, MEM_LEVEL);
+	if (WARN_ON_ONCE(wssize < 0))
+		return;
 	/* best-effort allocation; can be NULL */
-	stream.workspace = kmalloc(zlib_deflate_workspacesize(WINDOW_BITS, MEM_LEVEL),
-				   GFP_KERNEL);
+	stream.workspace = kmalloc(wssize, GFP_KERNEL);
 
 	/* touch memory so that pages are there in the case of a panic */
 	memset(qrbuf1, 0, sizeof(qrbuf1));
 	memset(qrbuf2, 0, sizeof(qrbuf2));
+	if (stream.workspace)
+		memset(stream.workspace, 0, wssize);
 }
 
 static void drm_panic_qr_exit(void)
-- 
2.55.0