From: Taehee Yoo ap420073@gmail.com
commit f5cd21605ecd249e5fc715411df22cc1bc877b32 upstream.
When module is being initialized, __init() calls bus_register() and driver_register(). These functions internally create various resources and sysfs files. The sysfs files are used for basic operations(add/del device). /sys/bus/netdevsim/new_device /sys/bus/netdevsim/del_device
These sysfs files use netdevsim resources, they are mostly allocated and initialized in ->probe() function, which is nsim_dev_probe(). But, sysfs files could be executed before ->probe() is finished. So, accessing uninitialized data would occur.
Another problem is very similar. /sys/bus/netdevsim/new_device internally creates sysfs files. /sys/devices/netdevsim<id>/new_port /sys/devices/netdevsim<id>/del_port
These sysfs files also use netdevsim resources, they are mostly allocated and initialized in creating device routine, which is nsim_bus_dev_new(). But they also could be executed before nsim_bus_dev_new() is finished. So, accessing uninitialized data would occur.
To fix these problems, this patch adds flags, which means whether the operation is finished or not. The flag variable 'nsim_bus_enable' means whether netdevsim bus was initialized or not. This is protected by nsim_bus_dev_list_lock. The flag variable 'nsim_bus_dev->init' means whether nsim_bus_dev was initialized or not. This could be used in {new/del}_port_store() with no lock.
Test commands: #SHELL1 modprobe netdevsim while : do echo "1 1" > /sys/bus/netdevsim/new_device echo "1 1" > /sys/bus/netdevsim/del_device done
#SHELL2 while : do echo 1 > /sys/devices/netdevsim1/new_port echo 1 > /sys/devices/netdevsim1/del_port done
Splat looks like: [ 47.508954][ T1008] general protection fault, probably for non-canonical address 0xdffffc0000000021: 0000 I [ 47.510793][ T1008] KASAN: null-ptr-deref in range [0x0000000000000108-0x000000000000010f] [ 47.511963][ T1008] CPU: 2 PID: 1008 Comm: bash Not tainted 5.5.0+ #322 [ 47.512823][ T1008] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 [ 47.514041][ T1008] RIP: 0010:__mutex_lock+0x10a/0x14b0 [ 47.514699][ T1008] Code: 08 84 d2 0f 85 7f 12 00 00 44 8b 0d 10 23 65 02 45 85 c9 75 29 49 8d 7f 68 48 b8 00 00 00 0f [ 47.517163][ T1008] RSP: 0018:ffff888059b4fbb0 EFLAGS: 00010206 [ 47.517802][ T1008] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 47.518941][ T1008] RDX: 0000000000000021 RSI: ffffffff85926440 RDI: 0000000000000108 [ 47.519732][ T1008] RBP: ffff888059b4fd30 R08: ffffffffc073fad0 R09: 0000000000000000 [ 47.520729][ T1008] R10: ffff888059b4fd50 R11: ffff88804bb38040 R12: 0000000000000000 [ 47.521702][ T1008] R13: dffffc0000000000 R14: ffffffff871976c0 R15: 00000000000000a0 [ 47.522760][ T1008] FS: 00007fd4be05a740(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000 [ 47.523877][ T1008] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 47.524627][ T1008] CR2: 0000561c82b69cf0 CR3: 0000000065dd6004 CR4: 00000000000606e0 [ 47.527662][ T1008] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 47.528604][ T1008] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 47.529531][ T1008] Call Trace: [ 47.529874][ T1008] ? nsim_dev_port_add+0x50/0x150 [netdevsim] [ 47.530470][ T1008] ? mutex_lock_io_nested+0x1380/0x1380 [ 47.531018][ T1008] ? _kstrtoull+0x76/0x160 [ 47.531449][ T1008] ? _parse_integer+0xf0/0xf0 [ 47.531874][ T1008] ? kernfs_fop_write+0x1cf/0x410 [ 47.532330][ T1008] ? sysfs_file_ops+0x160/0x160 [ 47.532773][ T1008] ? kstrtouint+0x86/0x110 [ 47.533168][ T1008] ? nsim_dev_port_add+0x50/0x150 [netdevsim] [ 47.533721][ T1008] nsim_dev_port_add+0x50/0x150 [netdevsim] [ 47.534336][ T1008] ? sysfs_file_ops+0x160/0x160 [ 47.534858][ T1008] new_port_store+0x99/0xb0 [netdevsim] [ 47.535439][ T1008] ? del_port_store+0xb0/0xb0 [netdevsim] [ 47.536035][ T1008] ? sysfs_file_ops+0x112/0x160 [ 47.536544][ T1008] ? sysfs_kf_write+0x3b/0x180 [ 47.537029][ T1008] kernfs_fop_write+0x276/0x410 [ 47.537548][ T1008] ? __sb_start_write+0x215/0x2e0 [ 47.538110][ T1008] vfs_write+0x197/0x4a0 [ ... ]
Fixes: f9d9db47d3ba ("netdevsim: add bus attributes to add new and delete devices") Fixes: 794b2c05ca1c ("netdevsim: extend device attrs to support port addition and deletion") Signed-off-by: Taehee Yoo ap420073@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/net/netdevsim/bus.c | 43 +++++++++++++++++++++++++++++++++++--- drivers/net/netdevsim/netdevsim.h | 1 2 files changed, 41 insertions(+), 3 deletions(-)
--- a/drivers/net/netdevsim/bus.c +++ b/drivers/net/netdevsim/bus.c @@ -17,6 +17,7 @@ static DEFINE_IDA(nsim_bus_dev_ids); static LIST_HEAD(nsim_bus_dev_list); static DEFINE_MUTEX(nsim_bus_dev_list_lock); +static bool nsim_bus_enable;
static struct nsim_bus_dev *to_nsim_bus_dev(struct device *dev) { @@ -99,6 +100,9 @@ new_port_store(struct device *dev, struc unsigned int port_index; int ret;
+ /* Prevent to use nsim_bus_dev before initialization. */ + if (!smp_load_acquire(&nsim_bus_dev->init)) + return -EBUSY; ret = kstrtouint(buf, 0, &port_index); if (ret) return ret; @@ -116,6 +120,9 @@ del_port_store(struct device *dev, struc unsigned int port_index; int ret;
+ /* Prevent to use nsim_bus_dev before initialization. */ + if (!smp_load_acquire(&nsim_bus_dev->init)) + return -EBUSY; ret = kstrtouint(buf, 0, &port_index); if (ret) return ret; @@ -179,15 +186,30 @@ new_device_store(struct bus_type *bus, c pr_err("Format for adding new device is "id port_count" (uint uint).\n"); return -EINVAL; } - nsim_bus_dev = nsim_bus_dev_new(id, port_count); - if (IS_ERR(nsim_bus_dev)) - return PTR_ERR(nsim_bus_dev);
mutex_lock(&nsim_bus_dev_list_lock); + /* Prevent to use resource before initialization. */ + if (!smp_load_acquire(&nsim_bus_enable)) { + err = -EBUSY; + goto err; + } + + nsim_bus_dev = nsim_bus_dev_new(id, port_count); + if (IS_ERR(nsim_bus_dev)) { + err = PTR_ERR(nsim_bus_dev); + goto err; + } + + /* Allow using nsim_bus_dev */ + smp_store_release(&nsim_bus_dev->init, true); + list_add_tail(&nsim_bus_dev->list, &nsim_bus_dev_list); mutex_unlock(&nsim_bus_dev_list_lock);
return count; +err: + mutex_unlock(&nsim_bus_dev_list_lock); + return err; } static BUS_ATTR_WO(new_device);
@@ -215,6 +237,11 @@ del_device_store(struct bus_type *bus, c
err = -ENOENT; mutex_lock(&nsim_bus_dev_list_lock); + /* Prevent to use resource before initialization. */ + if (!smp_load_acquire(&nsim_bus_enable)) { + mutex_unlock(&nsim_bus_dev_list_lock); + return -EBUSY; + } list_for_each_entry_safe(nsim_bus_dev, tmp, &nsim_bus_dev_list, list) { if (nsim_bus_dev->dev.id != id) continue; @@ -284,6 +311,8 @@ nsim_bus_dev_new(unsigned int id, unsign nsim_bus_dev->dev.type = &nsim_bus_dev_type; nsim_bus_dev->port_count = port_count; nsim_bus_dev->initial_net = current->nsproxy->net_ns; + /* Disallow using nsim_bus_dev */ + smp_store_release(&nsim_bus_dev->init, false);
err = device_register(&nsim_bus_dev->dev); if (err) @@ -299,6 +328,8 @@ err_nsim_bus_dev_free:
static void nsim_bus_dev_del(struct nsim_bus_dev *nsim_bus_dev) { + /* Disallow using nsim_bus_dev */ + smp_store_release(&nsim_bus_dev->init, false); device_unregister(&nsim_bus_dev->dev); ida_free(&nsim_bus_dev_ids, nsim_bus_dev->dev.id); kfree(nsim_bus_dev); @@ -320,6 +351,8 @@ int nsim_bus_init(void) err = driver_register(&nsim_driver); if (err) goto err_bus_unregister; + /* Allow using resources */ + smp_store_release(&nsim_bus_enable, true); return 0;
err_bus_unregister: @@ -331,12 +364,16 @@ void nsim_bus_exit(void) { struct nsim_bus_dev *nsim_bus_dev, *tmp;
+ /* Disallow using resources */ + smp_store_release(&nsim_bus_enable, false); + mutex_lock(&nsim_bus_dev_list_lock); list_for_each_entry_safe(nsim_bus_dev, tmp, &nsim_bus_dev_list, list) { list_del(&nsim_bus_dev->list); nsim_bus_dev_del(nsim_bus_dev); } mutex_unlock(&nsim_bus_dev_list_lock); + driver_unregister(&nsim_driver); bus_unregister(&nsim_bus); } --- a/drivers/net/netdevsim/netdevsim.h +++ b/drivers/net/netdevsim/netdevsim.h @@ -240,6 +240,7 @@ struct nsim_bus_dev { */ unsigned int num_vfs; struct nsim_vf_config *vfconfigs; + bool init; };
int nsim_bus_init(void);