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authorTakashi Iwai <tiwai@suse.de>2017-06-02 17:26:56 +0200
committerTakashi Iwai <tiwai@suse.de>2017-06-07 10:25:23 +0200
commitba3021b2c79b2fa9114f92790a99deb27a65b728 (patch)
treede2c41ab73193ebb84d87adb329c07d101ea2eb8 /sound
parentd11662f4f798b50d8c8743f433842c3e40fe3378 (diff)
ALSA: timer: Fix missing queue indices reset at SNDRV_TIMER_IOCTL_SELECT
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>
Diffstat (limited to 'sound')
-rw-r--r--sound/core/timer.c1
1 files changed, 1 insertions, 0 deletions
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);

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