snd_timer_user_tselect() reallocates the queue buffer dynamically, but it forgot to reset its indices. Since the read may happen concurrently with ioctl and snd_timer_user_tselect() allocates the buffer via kmalloc(), this may lead to the leak of uninitialized kernel-space data, as spotted via KMSAN:
BUG: KMSAN: use of unitialized memory in snd_timer_user_read+0x6c4/0xa10 CPU: 0 PID: 1037 Comm: probe Not tainted 4.11.0-rc5+ #2739 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 dump_stack+0x143/0x1b0 lib/dump_stack.c:52 kmsan_report+0x12a/0x180 mm/kmsan/kmsan.c:1007 kmsan_check_memory+0xc2/0x140 mm/kmsan/kmsan.c:1086 copy_to_user ./arch/x86/include/asm/uaccess.h:725 snd_timer_user_read+0x6c4/0xa10 sound/core/timer.c:2004 do_loop_readv_writev fs/read_write.c:716 __do_readv_writev+0x94c/0x1380 fs/read_write.c:864 do_readv_writev fs/read_write.c:894 vfs_readv fs/read_write.c:908 do_readv+0x52a/0x5d0 fs/read_write.c:934 SYSC_readv+0xb6/0xd0 fs/read_write.c:1021 SyS_readv+0x87/0xb0 fs/read_write.c:1018
This patch adds the missing reset of queue indices. Together with the previous fix for the ioctl/read race, we cover the whole problem.
Reported-by: Alexander Potapenko glider@google.com Tested-by: Alexander Potapenko glider@google.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/core/timer.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/sound/core/timer.c b/sound/core/timer.c index 1118bd8e2d3c..cd67d1c12cf1 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1618,6 +1618,7 @@ static int snd_timer_user_tselect(struct file *file, if (err < 0) goto __err;
+ tu->qhead = tu->qtail = tu->qused = 0; kfree(tu->queue); tu->queue = NULL; kfree(tu->tqueue);