[PATCH] ALSA: control: fix memory leak in snd_ctl_elem_read_user()

From: Johannes Weiner
Date: Thu Mar 21 2024 - 12:17:17 EST


With 6.9, I noticed kmalloc-2k blowing up to tens of gigabytes over
several days. Kmemleak shows a long string of these:

unreferenced object 0xffff8f1bddbce800 (size 2048):
comm "wireplumber", pid 1058, jiffies 4294690193
hex dump (first 32 bytes):
14 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00 ................
4d 61 73 74 65 72 20 50 6c 61 79 62 61 63 6b 20 Master Playback
backtrace (crc bd965d91):
[<ffffffff85ac328b>] __kmalloc_node_track_caller+0x25b/0x370
[<ffffffff85a79375>] memdup_user+0x25/0x80
[<ffffffff85fa5d63>] snd_ctl_ioctl+0x753/0x880
[<ffffffff85b18119>] __x64_sys_ioctl+0x89/0xb0
[<ffffffff861ee190>] do_syscall_64+0x80/0x170
[<ffffffff862000ab>] entry_SYSCALL_64_after_hwframe+0x46/0x4e

When 1052d9882269 ("ALSA: control: Use automatic cleanup of kfree()")
converted a few sites to automatic freeing, it removed the kfree from
snd_ctl_elem_read_user() but forgot to add the __free hook.

Fixes: 1052d9882269 ("ALSA: control: Use automatic cleanup of kfree()")
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
sound/core/control.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/core/control.c b/sound/core/control.c
index 8367fd485371..7da0d6afb766 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -1275,7 +1275,7 @@ static int snd_ctl_elem_read(struct snd_card *card,
static int snd_ctl_elem_read_user(struct snd_card *card,
struct snd_ctl_elem_value __user *_control)
{
- struct snd_ctl_elem_value *control;
+ struct snd_ctl_elem_value *control __free(kfree) = NULL;
int result;

control = memdup_user(_control, sizeof(*control));
--
2.44.0