[PATCH] HID: core: fix device cleanup on allocation failure

From: Tristan Madani <[email protected]>

hid_allocate_device() calls hid_destroy_device() in its error path when
hid_bpf_device_init() fails.  hid_destroy_device() in turn calls
hid_bpf_destroy_device() which invokes synchronize_srcu() and
cleanup_srcu_struct() on the SRCU structure.  However, at this point
init_srcu_struct() has not been called (or has failed), so the SRCU
internal pointers are all zeroed from kzalloc.  Dereferencing them
causes a general protection fault:

  general protection fault in check_init_srcu_struct
  KASAN: null-ptr-deref in range [0x00000000000001c0-0x00000000000001c7]
  Call Trace:
   synchronize_srcu+0x1c/0x2b0
   hid_bpf_destroy_device+0x64/0x90
   hid_destroy_device+0x29/0x240
   hid_allocate_device+0x420/0x4e0
   uhid_dev_create2+0x161/0x890

Fix this by replacing hid_destroy_device() with put_device() in the
error path.  At this point in hid_allocate_device(), the device has
been initialized (device_initialize) but not yet added (device_add),
so put_device() is the correct cleanup call.  It triggers the release
callback which frees the hid_device without attempting to clean up
resources that were never set up.

Found by syzkaller on Ubuntu 6.14.11 KASAN.

Fixes: 6cd735f0e57a ("HID: bpf: protect HID-BPF prog_list access by a SRCU")
Cc: [email protected]
Signed-off-by: Tristan Madani <[email protected]>
---
 drivers/hid/hid-core.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index cf123347a2af7..9534de5317783 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -3060,7 +3060,12 @@ struct hid_device *hid_allocate_device(void)
 	return hdev;
 
 out_err:
-	hid_destroy_device(hdev);
+	/*
+	 * hid_destroy_device() cannot be used here because
+	 * hid_bpf_device_init() failed and the SRCU struct was never
+	 * initialized.  Release the device directly.
+	 */
+	put_device(&hdev->dev);
 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(hid_allocate_device);
-- 
2.47.3