From 08aeb7c9a42ab7aa8b53c8f7779ec58f860a565c Mon Sep 17 00:00:00 2001 From: Jarod Wilson Date: Wed, 11 May 2011 15:14:31 -0300 Subject: [PATCH] [media] rc: add locking to fix register/show race When device_add is called in rc_register_device, the rc sysfs nodes show up, and there's a window in which ir-keytable can be launched via udev and trigger a show_protocols call, which runs without various rc_dev fields filled in yet. Add some locking around registration and store/show_protocols to prevent that from happening. The problem manifests thusly: [64692.957872] BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 [64692.957878] IP: [] show_protocols+0x47/0xf1 [rc_core] [64692.957890] PGD 19cfc7067 PUD 19cfc6067 PMD 0 [64692.957894] Oops: 0000 [#1] SMP [64692.957897] last sysfs file: /sys/devices/pci0000:00/0000:00:03.1/usb3/3-1/3-1:1.0/rc/rc2/protocols [64692.957902] CPU 3 [64692.957903] Modules linked in: redrat3(+) ir_lirc_codec lirc_dev ir_sony_decoder ir_jvc_decoder ir_rc6_decoder ir_rc5_decoder rc_hauppauge ir_nec _decoder rc_core ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables snd_emu10k1_synth snd_emux_synth snd_seq_virmidi snd_seq_mi di_event snd_seq_midi_emul snd_emu10k1 snd_rawmidi snd_ac97_codec ac97_bus snd_seq snd_pcm snd_seq_device snd_timer snd_page_alloc snd_util_mem pcsp kr tg3 snd_hwdep emu10k1_gp snd amd64_edac_mod gameport edac_core soundcore edac_mce_amd k8temp shpchp i2c_piix4 lm63 e100 mii uinput ipv6 raid0 rai d1 ata_generic firewire_ohci pata_acpi firewire_core crc_itu_t sata_svw pata_serverworks floppy radeon ttm drm_kms_helper drm i2c_algo_bit i2c_core [last unloaded: redrat3] [64692.957949] [64692.957952] Pid: 12265, comm: ir-keytable Tainted: G M W 2.6.39-rc6+ #2 empty empty/TYAN Thunder K8HM S3892 [64692.957957] RIP: 0010:[] [] show_protocols+0x47/0xf1 [rc_core] [64692.957962] RSP: 0018:ffff880194509e38 EFLAGS: 00010202 [64692.957964] RAX: 0000000000000000 RBX: ffffffffa036d1e0 RCX: ffffffffa036a47a [64692.957966] RDX: ffff88019a84d000 RSI: ffffffffa036d1e0 RDI: ffff88019cf2f3f0 [64692.957969] RBP: ffff880194509e68 R08: 0000000000000002 R09: 0000000000000000 [64692.957971] R10: 0000000000000002 R11: 0000000000001617 R12: ffff88019a84d000 [64692.957973] R13: 0000000000001000 R14: ffff8801944d2e38 R15: ffff88019ce5f190 [64692.957976] FS: 00007f0a30c9a720(0000) GS:ffff88019fc00000(0000) knlGS:0000000000000000 [64692.957979] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [64692.957981] CR2: 0000000000000090 CR3: 000000019a8e0000 CR4: 00000000000006e0 [64692.957983] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [64692.957986] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [64692.957989] Process ir-keytable (pid: 12265, threadinfo ffff880194508000, task ffff88019a9fc720) [64692.957991] Stack: [64692.957992] 0000000000000002 ffffffffa036d1e0 ffff880194509f58 0000000000001000 [64692.957997] ffff8801944d2e38 ffff88019ce5f190 ffff880194509e98 ffffffff8131484b [64692.958001] ffffffff8118e923 ffffffff810e9b2f ffff880194509e98 ffff8801944d2e18 [64692.958005] Call Trace: [64692.958014] [] dev_attr_show+0x27/0x4e [64692.958014] [] ? sysfs_read_file+0x94/0x172 [64692.958014] [] ? __get_free_pages+0x16/0x52 [64692.958014] [] sysfs_read_file+0xbd/0x172 [64692.958014] [] vfs_read+0xac/0xf3 [64692.958014] [] ? fget_light+0x3a/0xa1 [64692.958014] [] sys_read+0x4d/0x74 [64692.958014] [] system_call_fastpath+0x16/0x1b Its a bit difficult to reproduce, but I'm fairly confident this has fixed the problem. Signed-off-by: Jarod Wilson Signed-off-by: Mauro Carvalho Chehab --- drivers/media/rc/rc-main.c | 47 ++++++++++++++++++++++++++++++++++++++++------ include/media/rc-core.h | 7 +++++-- 2 files changed, 46 insertions(+), 8 deletions(-) diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c index a270664..0d4fcd9 100644 --- a/drivers/media/rc/rc-main.c +++ b/drivers/media/rc/rc-main.c @@ -749,6 +749,9 @@ static struct { * it is trigged by reading /sys/class/rc/rc?/protocols. * It returns the protocol names of supported protocols. * Enabled protocols are printed in brackets. + * + * dev->lock is taken to guard against races between device + * registration, store_protocols and show_protocols. */ static ssize_t show_protocols(struct device *device, struct device_attribute *mattr, char *buf) @@ -762,6 +765,8 @@ static ssize_t show_protocols(struct device *device, if (!dev) return -EINVAL; + mutex_lock(&dev->lock); + if (dev->driver_type == RC_DRIVER_SCANCODE) { enabled = dev->rc_map.rc_type; allowed = dev->allowed_protos; @@ -784,6 +789,9 @@ static ssize_t show_protocols(struct device *device, if (tmp != buf) tmp--; *tmp = '\n'; + + mutex_unlock(&dev->lock); + return tmp + 1 - buf; } @@ -802,6 +810,9 @@ static ssize_t show_protocols(struct device *device, * Writing "none" will disable all protocols. * Returns -EINVAL if an invalid protocol combination or unknown protocol name * is used, otherwise @len. + * + * dev->lock is taken to guard against races between device + * registration, store_protocols and show_protocols. */ static ssize_t store_protocols(struct device *device, struct device_attribute *mattr, @@ -815,18 +826,22 @@ static ssize_t store_protocols(struct device *device, u64 mask; int rc, i, count = 0; unsigned long flags; + ssize_t ret; /* Device is being removed */ if (!dev) return -EINVAL; + mutex_lock(&dev->lock); + if (dev->driver_type == RC_DRIVER_SCANCODE) type = dev->rc_map.rc_type; else if (dev->raw) type = dev->raw->enabled_protocols; else { IR_dprintk(1, "Protocol switching not supported\n"); - return -EINVAL; + ret = -EINVAL; + goto out; } while ((tmp = strsep((char **) &data, " \n")) != NULL) { @@ -860,7 +875,8 @@ static ssize_t store_protocols(struct device *device, } if (i == ARRAY_SIZE(proto_names)) { IR_dprintk(1, "Unknown protocol: '%s'\n", tmp); - return -EINVAL; + ret = -EINVAL; + goto out; } count++; } @@ -875,7 +891,8 @@ static ssize_t store_protocols(struct device *device, if (!count) { IR_dprintk(1, "Protocol not specified\n"); - return -EINVAL; + ret = -EINVAL; + goto out; } if (dev->change_protocol) { @@ -883,7 +900,8 @@ static ssize_t store_protocols(struct device *device, if (rc < 0) { IR_dprintk(1, "Error setting protocols to 0x%llx\n", (long long)type); - return -EINVAL; + ret = -EINVAL; + goto out; } } @@ -898,7 +916,11 @@ static ssize_t store_protocols(struct device *device, IR_dprintk(1, "Current protocol(s): 0x%llx\n", (long long)type); - return len; + ret = len; + +out: + mutex_unlock(&dev->lock); + return ret; } static void rc_dev_release(struct device *device) @@ -974,6 +996,7 @@ struct rc_dev *rc_allocate_device(void) spin_lock_init(&dev->rc_map.lock); spin_lock_init(&dev->keylock); + mutex_init(&dev->lock); setup_timer(&dev->timer_keyup, ir_timer_keyup, (unsigned long)dev); dev->dev.type = &rc_dev_type; @@ -1019,12 +1042,21 @@ int rc_register_device(struct rc_dev *dev) if (dev->close) dev->input_dev->close = ir_close; + /* + * Take the lock here, as the device sysfs node will appear + * when device_add() is called, which may trigger an ir-keytable udev + * rule, which will in turn call show_protocols and access either + * dev->rc_map.rc_type or dev->raw->enabled_protocols before it has + * been initialized. + */ + mutex_lock(&dev->lock); + dev->devno = (unsigned long)(atomic_inc_return(&devno) - 1); dev_set_name(&dev->dev, "rc%ld", dev->devno); dev_set_drvdata(&dev->dev, dev); rc = device_add(&dev->dev); if (rc) - return rc; + goto out_unlock; rc = ir_setkeytable(dev, rc_map); if (rc) @@ -1058,6 +1090,7 @@ int rc_register_device(struct rc_dev *dev) if (rc < 0) goto out_input; } + mutex_unlock(&dev->lock); if (dev->change_protocol) { rc = dev->change_protocol(dev, rc_map->rc_type); @@ -1083,6 +1116,8 @@ out_table: ir_free_table(&dev->rc_map); out_dev: device_del(&dev->dev); +out_unlock: + mutex_unlock(&dev->lock); return rc; } EXPORT_SYMBOL_GPL(rc_register_device); diff --git a/include/media/rc-core.h b/include/media/rc-core.h index 2963263..60536c7 100644 --- a/include/media/rc-core.h +++ b/include/media/rc-core.h @@ -40,10 +40,12 @@ enum rc_driver_type { * @driver_name: name of the hardware driver which registered this device * @map_name: name of the default keymap * @rc_map: current scan/key table + * @lock: used to ensure we've filled in all protocol details before + * anyone can call show_protocols or store_protocols * @devno: unique remote control device number * @raw: additional data for raw pulse/space devices * @input_dev: the input child device used to communicate events to userspace - * @driver_type: specifies if protocol decoding is done in hardware or software + * @driver_type: specifies if protocol decoding is done in hardware or software * @idle: used to keep track of RX state * @allowed_protos: bitmask with the supported RC_TYPE_* protocols * @scanmask: some hardware decoders are not capable of providing the full @@ -86,7 +88,8 @@ struct rc_dev { struct input_id input_id; char *driver_name; const char *map_name; - struct rc_map rc_map; + struct rc_map rc_map; + struct mutex lock; unsigned long devno; struct ir_raw_event_ctrl *raw; struct input_dev *input_dev; -- 2.7.4