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| author | Gaosheng Cui <cuigaosheng1@huawei.com> | 2022-12-02 14:06:33 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-01-19 16:24:04 +0100 |
| commit | 5abbeebd8296c2301023b8dc4b5a6c0d5229b4f5 (patch) | |
| tree | 5473994be1f214f01793c68bcdfd6695d827cce7 /drivers/accessibility | |
| parent | f24771b62a83239f0dce816bddf0f6807f436235 (diff) | |
| download | lwn-5abbeebd8296c2301023b8dc4b5a6c0d5229b4f5.tar.gz lwn-5abbeebd8296c2301023b8dc4b5a6c0d5229b4f5.zip | |
tty: fix possible null-ptr-defer in spk_ttyio_release
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>
Diffstat (limited to 'drivers/accessibility')
| -rw-r--r-- | drivers/accessibility/speakup/spk_ttyio.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/accessibility/speakup/spk_ttyio.c b/drivers/accessibility/speakup/spk_ttyio.c index 08cf8a17754b..07373b3debd1 100644 --- 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 *in_synth) { struct tty_struct *tty = in_synth->dev; + if (tty == NULL) + return; + tty_lock(tty); if (tty->ops->close) |