Hi Matias, > Fix crash caused by NULL pointer dereference when debugfs functions > le_max_key_read, le_max_key_size_write, le_min_key_size_read or > le_min_key_size_write and Bluetooth adapter was powered off. > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201253 > > BUG: unable to handle kernel NULL pointer dereference at 00000000000002e8 > PGD 0 P4D 0 > Oops: 0000 [#24] SMP PTI > CPU: 2 PID: 6255 Comm: cat Tainted: G D OE 4.18.9-200.fc28.x86_64 #1 > Hardware name: LENOVO 4286CTO/4286CTO, BIOS 8DET76WW (1.46 ) 06/21/2018 > RIP: 0010:le_max_key_size_read+0x45/0xb0 [bluetooth] > Code: 00 00 00 48 83 ec 10 65 48 8b 04 25 28 00 00 00 48 89 44 24 08 31 c0 48 8b 87 c8 00 00 00 48 8d 7c 24 04 48 8b 80 48 0a 00 00 <48> 8b 80 e8 02 00 00 0f b6 48 52 e8 fb b6 b3 ed be 04 00 00 00 48 > RSP: 0018:ffffab23c3ff3df0 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: 00007f0b4ca2e000 RCX: ffffab23c3ff3f08 > RDX: ffffffffc0ddb033 RSI: 0000000000000004 RDI: ffffab23c3ff3df4 > RBP: 0000000000020000 R08: 0000000000000000 R09: 0000000000000000 > R10: ffffab23c3ff3ed8 R11: 0000000000000000 R12: ffffab23c3ff3f08 > R13: 00007f0b4ca2e000 R14: 0000000000020000 R15: ffffab23c3ff3f08 > FS: 00007f0b4ca0f540(0000) GS:ffff91bd5e280000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00000000000002e8 CR3: 00000000629fa006 CR4: 00000000000606e0 > Call Trace: > full_proxy_read+0x53/0x80 > __vfs_read+0x36/0x180 > vfs_read+0x8a/0x140 > ksys_read+0x4f/0xb0 > do_syscall_64+0x5b/0x160 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Signed-off-by: Matias Karhumaa <matias.karhumaa@xxxxxxxxx> > --- > net/bluetooth/smp.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 57 insertions(+), 5 deletions(-) > > diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c > index 3a7b077..0da3754 100644 > --- a/net/bluetooth/smp.c > +++ b/net/bluetooth/smp.c > @@ -3368,9 +3368,22 @@ static ssize_t le_min_key_size_read(struct file *file, > size_t count, loff_t *ppos) > { > struct hci_dev *hdev = file->private_data; > + struct l2cap_chan *chan; > + struct smp_dev *smp; > char buf[4]; > > - snprintf(buf, sizeof(buf), "%2u\n", SMP_DEV(hdev)->min_key_size); > + if (!hdev) > + return -EFAULT; the -EFAULT is never the right error unless you have some memory access error. And frankly I have no idea what you are checking !hdev here. If that would ever happen, then we have serious other problems. > + > + chan = hdev->smp_data; > + if (!chan) > + return -EFAULT; > + > + smp = chan->data; > + if (!smp) > + return -EFAULT; > + > + snprintf(buf, sizeof(buf), "%2u\n", smp->min_key_size); > > return simple_read_from_buffer(user_buf, count, ppos, buf, strlen(buf)); > } > @@ -3380,10 +3393,23 @@ static ssize_t le_min_key_size_write(struct file *file, > size_t count, loff_t *ppos) > { > struct hci_dev *hdev = file->private_data; > + struct l2cap_chan *chan; > + struct smp_dev *smp; > char buf[32]; > size_t buf_size = min(count, (sizeof(buf) - 1)); > u8 key_size; > > + if (!hdev) > + return -EFAULT; > + > + chan = hdev->smp_data; > + if (!chan) > + return -EFAULT; > + > + smp = chan->data; > + if (!smp) > + return -EFAULT; > + > if (copy_from_user(buf, user_buf, buf_size)) > return -EFAULT; > > @@ -3391,11 +3417,11 @@ static ssize_t le_min_key_size_write(struct file *file, > > sscanf(buf, "%hhu", &key_size); > > - if (key_size > SMP_DEV(hdev)->max_key_size || > + if (key_size > smp->max_key_size || > key_size < SMP_MIN_ENC_KEY_SIZE) > return -EINVAL; > > - SMP_DEV(hdev)->min_key_size = key_size; > + smp->min_key_size = key_size; Maybe we just need to store min and max key sizes in hdev instead of trying to store them in the SMP object. Maybe Johan has some other idea, but I think that debugfs command should always work and remember the value even when SMP gets only created later. Regards Marcel
