From: Gaosheng Cui cuigaosheng1@huawei.com
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@kernel.org Signed-off-by: Gaosheng Cui cuigaosheng1@huawei.com Link: https://lore.kernel.org/r/20221202060633.217364-1-cuigaosheng1@huawei.com Reviewed-by: Samuel Thibault samuel.thibault@ens-lyon.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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)