From: Gaosheng Cui <cuigaosheng1@xxxxxxxxxx>
commit 5abbeebd8296c2301023b8dc4b5a6c0d5229b4f5 upstream.
Run the following tests on the qemu platform:
syzkaller:~# modprobe speakup_audptr
input: Speakup as /devices/virtual/input/input4
initialized device: /dev/synth, node (MAJOR 10, MINOR 125)
speakup 3.1.6: initialized
synth name on entry is: (null)
synth probe
spk_ttyio_initialise_ldisc failed because tty_kopen_exclusive returned
failed (errno -16), then remove the module, we will get a null-ptr-defer
problem, as follow:
syzkaller:~# modprobe -r speakup_audptr
releasing synth audptr
BUG: kernel NULL pointer dereference, address: 0000000000000080
#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: 2 PID: 204 Comm: modprobe Not tainted 6.1.0-rc6-dirty #1
RIP: 0010:mutex_lock+0x14/0x30
Call Trace:
<TASK>
spk_ttyio_release+0x19/0x70 [speakup]
synth_release.part.6+0xac/0xc0 [speakup]
synth_remove+0x56/0x60 [speakup]
__x64_sys_delete_module+0x156/0x250
? fpregs_assert_state_consistent+0x1d/0x50
do_syscall_64+0x37/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd
</TASK>
Modules linked in: speakup_audptr(-) speakup
Dumping ftrace buffer:
in_synth->dev was not initialized during modprobe, so we add check
for in_synth->dev to fix this bug.
Fixes: 4f2a81f3a882 ("speakup: Reference synth from tty and tty from synth")
Cc: stable <stable@xxxxxxxxxx>
Signed-off-by: Gaosheng Cui <cuigaosheng1@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221202060633.217364-1-cuigaosheng1@xxxxxxxxxx
Reviewed-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/accessibility/speakup/spk_ttyio.c | 3 +++
1 file changed, 3 insertions(+)
--- a/drivers/accessibility/speakup/spk_ttyio.c
+++ b/drivers/accessibility/speakup/spk_ttyio.c
@@ -354,6 +354,9 @@ void spk_ttyio_release(struct spk_synth
{
struct tty_struct *tty = in_synth->dev;
+ if (tty == NULL)
+ return;
+
tty_lock(tty);
if (tty->ops->close)
