[PATCH 6.0 0469/1073] ALSA: mts64: fix possible null-ptr-defer in snd_mts64_interrupt

Greg Kroah-Hartman
2022-12-28T15:55:17Z

From: Gaosheng Cui <cuigaosheng1@huawei.com>

[ Upstream commit cf2ea3c86ad90d63d1c572b43e1ca9276b0357ad ]

I got a null-ptr-defer error report when I do the following tests
on the qemu platform:

make defconfig and CONFIG_PARPORT=m, CONFIG_PARPORT_PC=m,
CONFIG_SND_MTS64=m

Then making test scripts:
cat>test_mod1.sh<<EOF
modprobe snd-mts64
modprobe snd-mts64
EOF

Executing the script, perhaps several times, we will get a null-ptr-defer
report, as follow:

syzkaller:~# ./test_mod.sh
snd_mts64: probe of snd_mts64.0 failed with error -5
modprobe: ERROR: could not insert 'snd_mts64': No such device
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 0 P4D 0
Oops: 0002 [#1] PREEMPT SMP PTI
CPU: 0 PID: 205 Comm: modprobe Not tainted 6.1.0-rc8-00588-g76dcd734eca2 #6
Call Trace:
<IRQ>
snd_mts64_interrupt+0x24/0xa0 [snd_mts64]
parport_irq_handler+0x37/0x50 [parport]
__handle_irq_event_percpu+0x39/0x190
handle_irq_event_percpu+0xa/0x30
handle_irq_event+0x2f/0x50
handle_edge_irq+0x99/0x1b0
__common_interrupt+0x5d/0x100
common_interrupt+0xa0/0xc0
</IRQ>
<TASK>
asm_common_interrupt+0x22/0x40
RIP: 0010:_raw_write_unlock_irqrestore+0x11/0x30
parport_claim+0xbd/0x230 [parport]
snd_mts64_probe+0x14a/0x465 [snd_mts64]
platform_probe+0x3f/0xa0
really_probe+0x129/0x2c0
__driver_probe_device+0x6d/0xc0
driver_probe_device+0x1a/0xa0
__device_attach_driver+0x7a/0xb0
bus_for_each_drv+0x62/0xb0
__device_attach+0xe4/0x180
bus_probe_device+0x82/0xa0
device_add+0x550/0x920
platform_device_add+0x106/0x220
snd_mts64_attach+0x2e/0x80 [snd_mts64]
port_check+0x14/0x20 [parport]
bus_for_each_dev+0x6e/0xc0
__parport_register_driver+0x7c/0xb0 [parport]
snd_mts64_module_init+0x31/0x1000 [snd_mts64]
do_one_initcall+0x3c/0x1f0
do_init_module+0x46/0x1c6
load_module+0x1d8d/0x1e10
__do_sys_finit_module+0xa2/0xf0
do_syscall_64+0x37/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd
</TASK>
Kernel panic - not syncing: Fatal exception in interrupt
Rebooting in 1 seconds..

The mts wa not initialized during interrupt, we add check for
mts to fix this bug.

Fixes: 68ab801e32bb ("[ALSA] Add snd-mts64 driver for ESI Miditerminal 4140")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Link: https://lore.kernel.org/r/20221206061004.1222966-1-cuigaosheng1@huawei.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
sound/drivers/mts64.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/sound/drivers/mts64.c b/sound/drivers/mts64.c
index d3bc9e8c407d..f0d34cf70c3e 100644
--- a/sound/drivers/mts64.c
+++ b/sound/drivers/mts64.c
@@ -815,6 +815,9 @@ static void snd_mts64_interrupt(void *private)
u8 status, data;
struct snd_rawmidi_substream *substream;

+ if (!mts)
+ return;
+
spin_lock(&mts->lock);
ret = mts64_read(mts->pardev->port);
data = ret & 0x00ff;
--
2.35.1