Jason has been running Syzkaller that reported the following bug:
sysfs: cannot create duplicate filename '/devices/iommufd_mock4'
Call Trace:
sysfs_warn_dup+0x71/0x90
sysfs_create_dir_ns+0x1ee/0x260
? sysfs_create_mount_point+0x80/0x80
? spin_bug+0x1d0/0x1d0
? do_raw_spin_unlock+0x54/0x220
kobject_add_internal+0x221/0x970
kobject_add+0x11c/0x1e0
? lockdep_hardirqs_on_prepare+0x273/0x3e0
? kset_create_and_add+0x160/0x160
? kobject_put+0x5d/0x390
? bus_get_dev_root+0x4a/0x60
? kobject_put+0x5d/0x390
device_add+0x1d5/0x1550
? __fw_devlink_link_to_consumers.isra.0+0x1f0/0x1f0
? __init_waitqueue_head+0xcb/0x150
iommufd_test+0x462/0x3b60
? lock_release+0x1fe/0x640
? __might_fault+0x117/0x170
? reacquire_held_locks+0x4b0/0x4b0
? iommufd_selftest_destroy+0xd0/0xd0
? __might_fault+0xbe/0x170
iommufd_fops_ioctl+0x256/0x350
? iommufd_option+0x180/0x180
? __lock_acquire+0x1755/0x45f0
__x64_sys_ioctl+0xa13/0x1640
The bug is triggered when Syzkaller created multiple mock devices but
didn't destroy them in the same sequence, messing up the mock_dev_num
counter. So, fix it with a mock_dev_ida.
Fixes: 23a1b46f15d5 ("iommufd/selftest: Make the mock iommu driver into a real driver")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
---
drivers/iommu/iommufd/selftest.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
index 8abf9747773e..2bfe77bd351d 100644
--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -36,7 +36,7 @@ static struct mock_bus_type iommufd_mock_bus_type = {
},
};
-static atomic_t mock_dev_num;
+static DEFINE_IDA(mock_dev_ida);
enum {
MOCK_DIRTY_TRACK = 1,
@@ -123,6 +123,7 @@ enum selftest_obj_type {
struct mock_dev {
struct device dev;
unsigned long flags;
+ int id;
};
struct selftest_obj {
@@ -631,7 +632,7 @@ static void mock_dev_release(struct device *dev)
{
struct mock_dev *mdev = container_of(dev, struct mock_dev, dev);
- atomic_dec(&mock_dev_num);
+ ida_free(&mock_dev_ida, mdev->id);
kfree(mdev);
}
@@ -653,8 +654,12 @@ static struct mock_dev *mock_dev_create(unsigned long dev_flags)
mdev->dev.release = mock_dev_release;
mdev->dev.bus = &iommufd_mock_bus_type.bus;
- rc = dev_set_name(&mdev->dev, "iommufd_mock%u",
- atomic_inc_return(&mock_dev_num));
+ rc = ida_alloc(&mock_dev_ida, GFP_KERNEL);
+ if (rc < 0)
+ goto err_put;
+ mdev->id = rc;
+
+ rc = dev_set_name(&mdev->dev, "iommufd_mock%u", mdev->id);
if (rc)
goto err_put;
--
2.43.0
