KMSAN: uninit-value in get_min_max_with_quirks

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c2453450 kmsan: kcov: prettify the code unpoisoning area->..
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=119f1173600000
kernel config: https://syzkaller.appspot.com/x/.config?x=3684f3c73f43899a
dashboard link: https://syzkaller.appspot.com/bug?extid=abe1ab7afc62c6bb6377
compiler: clang version 9.0.0 (/home/glider/llvm/clang
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16255fe7600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15e73290e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+abe1ab...@syzkaller.appspotmail.com

usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-1: Product: syz
usb 1-1: Manufacturer: syz
usb 1-1: SerialNumber: syz
usb 1-1: 0:2 : does not exist
=====================================================
BUG: KMSAN: uninit-value in get_min_max_with_quirks+0xd6f/0x2ea0
sound/usb/mixer.c:1239
CPU: 0 PID: 2859 Comm: kworker/0:2 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x191/0x1f0 lib/dump_stack.c:113
kmsan_report+0x14a/0x2f0 mm/kmsan/kmsan_report.c:109
__msan_warning+0x73/0xf0 mm/kmsan/kmsan_instr.c:245
get_min_max_with_quirks+0xd6f/0x2ea0 sound/usb/mixer.c:1239
__build_feature_ctl+0x12b9/0x29e0 sound/usb/mixer.c:1665
build_feature_ctl sound/usb/mixer.c:1709 [inline]
parse_audio_feature_unit sound/usb/mixer.c:1918 [inline]
parse_audio_unit+0x218c/0x7490 sound/usb/mixer.c:2753
snd_usb_mixer_controls sound/usb/mixer.c:3095 [inline]
snd_usb_create_mixer+0x1d7c/0x4070 sound/usb/mixer.c:3445
usb_audio_probe+0x286b/0x3eb0 sound/usb/card.c:653
usb_probe_interface+0xd19/0x1310 drivers/usb/core/driver.c:361
really_probe+0xd91/0x1f90 drivers/base/dd.c:552
driver_probe_device+0x1ba/0x510 drivers/base/dd.c:721
__device_attach_driver+0x5b8/0x790 drivers/base/dd.c:828
bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:430
__device_attach+0x489/0x750 drivers/base/dd.c:894
device_initial_probe+0x4a/0x60 drivers/base/dd.c:941
bus_probe_device+0x131/0x390 drivers/base/bus.c:490
device_add+0x25b5/0x2df0 drivers/base/core.c:2201
usb_set_configuration+0x309f/0x3710 drivers/usb/core/message.c:2027
generic_probe+0xe7/0x280 drivers/usb/core/generic.c:210
usb_probe_device+0x146/0x200 drivers/usb/core/driver.c:266
really_probe+0xd91/0x1f90 drivers/base/dd.c:552
driver_probe_device+0x1ba/0x510 drivers/base/dd.c:721
__device_attach_driver+0x5b8/0x790 drivers/base/dd.c:828
bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:430
__device_attach+0x489/0x750 drivers/base/dd.c:894
device_initial_probe+0x4a/0x60 drivers/base/dd.c:941
bus_probe_device+0x131/0x390 drivers/base/bus.c:490
device_add+0x25b5/0x2df0 drivers/base/core.c:2201
usb_new_device+0x23e5/0x2fb0 drivers/usb/core/hub.c:2536
hub_port_connect drivers/usb/core/hub.c:5098 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
port_event drivers/usb/core/hub.c:5359 [inline]
hub_event+0x581d/0x72f0 drivers/usb/core/hub.c:5441
process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
kthread+0x4b5/0x4f0 kernel/kthread.c:256
ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Local variable description: ----saved@get_min_max_with_quirks
Variable was created at:
get_min_max_with_quirks+0xa8b/0x2ea0 sound/usb/mixer.c:1231
get_min_max_with_quirks+0xa8b/0x2ea0 sound/usb/mixer.c:1231
=====================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
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syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Takashi Iwai]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git topic/usb-fix

[syzbot]

> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git
> topic/usb-fix

KMSAN bugs can only be tested on https://github.com/google/kmsan.git tree
because KMSAN tool is not upstreamed yet.
See https://goo.gl/tpsmEJ#kmsan-bugs for details.

[Takashi Iwai]

#syz test: https://github.com/google/kmsan.git master

-- 8< --
From: Takashi Iwai <ti...@suse.de>
Subject: [PATCH] ALSA: usb-audio: Fix missing error check at mixer resolution
test

A check of the return value from get_cur_mix_raw() is missing at the
resolution test code in get_min_max_with_quirks(), which may leave the
variable untouched, leading to a random uninitialized value, as
detected by syzkaller fuzzer.

Add the missing return error check for fixing that.

Reported-by: syzbot+abe1ab...@syzkaller.appspotmail.com
Cc: <sta...@vger.kernel.org>
Signed-off-by: Takashi Iwai <ti...@suse.de>
---
sound/usb/mixer.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 3fd1d1749edf..45eee5cc312e 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1229,7 +1229,8 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
if (cval->min + cval->res < cval->max) {
int last_valid_res = cval->res;
int saved, test, check;
- get_cur_mix_raw(cval, minchn, &saved);
+ if (get_cur_mix_raw(cval, minchn, &saved) < 0)
+ goto no_res_check;
for (;;) {
test = saved;
if (test < cval->max)
@@ -1249,6 +1250,7 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
snd_usb_set_cur_mix_value(cval, minchn, 0, saved);
}

+no_res_check:
cval->initialized = 1;
}

--
2.16.4

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger
crash:

Reported-and-tested-by:
syzbot+abe1ab...@syzkaller.appspotmail.com

Tested on:

commit: e741088f stackdepot: remove code preventing compiler optim..

git tree: https://github.com/google/kmsan.git master

kernel config: https://syzkaller.appspot.com/x/.config?x=9e324dfe9c7b0360

dashboard link: https://syzkaller.appspot.com/bug?extid=abe1ab7afc62c6bb6377
compiler: clang version 9.0.0 (/home/glider/llvm/clang
80fee25776c2fb61e74c1ecb1a523375c2500b69)

patch: https://syzkaller.appspot.com/x/patch.diff?x=102fe2e8e00000

Note: testing is done by a robot and is best-effort only.