From: "He, Bo" <bo.he@xxxxxxxxx> [ Upstream commit cef0d4948cb0a02db37ebfdc320e127c77ab1637 ] There is a race condition that could happen if hid_debug_rdesc_show() is running while hdev is in the process of going away (device removal, system suspend, etc) which could result in NULL pointer dereference: BUG: unable to handle kernel paging request at 0000000783316040 CPU: 1 PID: 1512 Comm: getevent Tainted: G U O 4.19.20-quilt-2e5dc0ac-00029-gc455a447dd55 #1 RIP: 0010:hid_dump_device+0x9b/0x160 Call Trace: hid_debug_rdesc_show+0x72/0x1d0 seq_read+0xe0/0x410 full_proxy_read+0x5f/0x90 __vfs_read+0x3a/0x170 vfs_read+0xa0/0x150 ksys_read+0x58/0xc0 __x64_sys_read+0x1a/0x20 do_syscall_64+0x55/0x110 entry_SYSCALL_64_after_hwframe+0x49/0xbe Grab driver_input_lock to make sure the input device exists throughout the whole process of dumping the rdesc. [jkosina@xxxxxxx: update changelog a bit] Signed-off-by: "he, bo" <bo.he@xxxxxxxxx> Signed-off-by: "Zhang, Jun" <jun.zhang@xxxxxxxxx> Signed-off-by: Jiri Kosina <jkosina@xxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/hid/hid-debug.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c index ebc9ffde41e9..a353a011fbdf 100644 --- a/drivers/hid/hid-debug.c +++ b/drivers/hid/hid-debug.c @@ -1060,10 +1060,15 @@ static int hid_debug_rdesc_show(struct seq_file *f, void *p) seq_printf(f, "\n\n"); /* dump parsed data and input mappings */ + if (down_interruptible(&hdev->driver_input_lock)) + return 0; + hid_dump_device(hdev, f); seq_printf(f, "\n"); hid_dump_input_mapping(hdev, f); + up(&hdev->driver_input_lock); + return 0; } -- 2.19.1
