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Subject[PATCH] ALSA: mixart: Reduce size of mixart_timer_notify
Date
The mixart_timer_notify structure was larger than could be represented
by the mixart_msg_data array storage. Adjust the size to as large as
possible to fix the warning seen with -Warray-bounds builds:

sound/pci/mixart/mixart_core.c: In function 'snd_mixart_threaded_irq':
sound/pci/mixart/mixart_core.c:447:50: error: array subscript 'struct mixart_timer_notify[0]' is partly outside array bounds of 'u32[128]' {aka 'unsigned int[128]'} [-Werror=array-bounds]
447 | for(i=0; i<notify->stream_count; i++) {
| ^~
sound/pci/mixart/mixart_core.c:328:12: note: while referencing 'mixart_msg_data'
328 | static u32 mixart_msg_data[MSG_DEFAULT_SIZE / 4];
| ^~~~~~~~~~~~~~~

Signed-off-by: Kees Cook <keescook@chromium.org>
---
sound/pci/mixart/mixart_core.c | 3 +--
sound/pci/mixart/mixart_core.h | 10 +++++++++-
2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/sound/pci/mixart/mixart_core.c b/sound/pci/mixart/mixart_core.c
index fb8895af0363..853083dd4bad 100644
--- a/sound/pci/mixart/mixart_core.c
+++ b/sound/pci/mixart/mixart_core.c
@@ -23,8 +23,6 @@
#define MSG_DESCRIPTOR_SIZE 0x24
#define MSG_HEADER_SIZE (MSG_DESCRIPTOR_SIZE + 4)

-#define MSG_DEFAULT_SIZE 512
-
#define MSG_TYPE_MASK 0x00000003 /* mask for following types */
#define MSG_TYPE_NOTIFY 0 /* embedded -> driver (only notification, do not get_msg() !) */
#define MSG_TYPE_COMMAND 1 /* driver <-> embedded (a command has no answer) */
@@ -444,6 +442,7 @@ irqreturn_t snd_mixart_threaded_irq(int irq, void *dev_id)
struct mixart_timer_notify *notify;
notify = (struct mixart_timer_notify *)mixart_msg_data;

+ BUILD_BUG_ON(sizeof(notify) > sizeof(mixart_msg_data));
for(i=0; i<notify->stream_count; i++) {

u32 buffer_id = notify->streams[i].buffer_id;
diff --git a/sound/pci/mixart/mixart_core.h b/sound/pci/mixart/mixart_core.h
index fbf4731a276d..2f0e29ed5d63 100644
--- a/sound/pci/mixart/mixart_core.h
+++ b/sound/pci/mixart/mixart_core.h
@@ -49,6 +49,7 @@ enum mixart_message_id {
MSG_CLOCK_SET_PROPERTIES = 0x200002,
};

+#define MSG_DEFAULT_SIZE 512

struct mixart_msg
{
@@ -251,10 +252,17 @@ struct mixart_sample_pos
u32 sample_pos_low_part;
} __attribute__((packed));

+/*
+ * This structure is limited by the size of MSG_DEFAULT_SIZE. Instead of
+ * having MIXART_MAX_STREAM_PER_CARD * MIXART_MAX_CARDS many streams,
+ * this is capped to have a total size below MSG_DEFAULT_SIZE.
+ */
+#define MIXART_MAX_TIMER_NOTIFY_STREAMS \
+ ((MSG_DEFAULT_SIZE - sizeof(u32)) / sizeof(struct mixart_sample_pos))
struct mixart_timer_notify
{
u32 stream_count;
- struct mixart_sample_pos streams[MIXART_MAX_STREAM_PER_CARD * MIXART_MAX_CARDS];
+ struct mixart_sample_pos streams[MIXART_MAX_TIMER_NOTIFY_STREAMS];
} __attribute__((packed));


--
2.30.2
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