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The driver checks port->exists twice in i8042_interrupt(), first when trying to assign temporary "serio" variable, and second time when deciding whether it should call serio_interrupt(). The value of port->exists may change between the 2 checks, and we may end up calling serio_interrupt() with a NULL pointer: BUG: unable to handle kernel NULL pointer dereference at 0000000000000050 IP: [<ffffffff8150feaf>] _spin_lock_irqsave+0x1f/0x40 PGD 0 Oops: 0002 [#1] SMP last sysfs file: CPU 0 Modules linked in: Pid: 1, comm: swapper Not tainted 2.6.32-358.el6.x86_64 #1 QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:[<ffffffff8150feaf>] [<ffffffff8150feaf>] _spin_lock_irqsave+0x1f/0x40 RSP: 0018:ffff880028203cc0 EFLAGS: 00010082 RAX: 0000000000010000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000282 RSI: 0000000000000098 RDI: 0000000000000050 RBP: ffff880028203cc0 R08: ffff88013e79c000 R09: ffff880028203ee0 R10: 0000000000000298 R11: 0000000000000282 R12: 0000000000000050 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000098 FS: 0000000000000000(0000) GS:ffff880028200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b CR2: 0000000000000050 CR3: 0000000001a85000 CR4: 00000000001407f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process swapper (pid: 1, threadinfo ffff88013e79c000, task ffff88013e79b500) Stack: ffff880028203d00 ffffffff813de186 ffffffffffffff02 0000000000000000 <d> 0000000000000000 0000000000000000 0000000000000000 0000000000000098 <d> ffff880028203d70 ffffffff813e0162 ffff880028203d20 ffffffff8103b8ac Call Trace: <IRQ> [<ffffffff813de186>] serio_interrupt+0x36/0xa0 [<ffffffff813e0162>] i8042_interrupt+0x132/0x3a0 [<ffffffff8103b8ac>] ? kvm_clock_read+0x1c/0x20 [<ffffffff8103b8b9>] ? kvm_clock_get_cycles+0x9/0x10 [<ffffffff810e1640>] handle_IRQ_event+0x60/0x170 [<ffffffff8103b154>] ? kvm_guest_apic_eoi_write+0x44/0x50 [<ffffffff810e3d8e>] handle_edge_irq+0xde/0x180 [<ffffffff8100de89>] handle_irq+0x49/0xa0 [<ffffffff81516c8c>] do_IRQ+0x6c/0xf0 [<ffffffff8100b9d3>] ret_from_intr+0x0/0x11 [<ffffffff81076f63>] ? __do_softirq+0x73/0x1e0 [<ffffffff8109b75b>] ? hrtimer_interrupt+0x14b/0x260 [<ffffffff8100c1cc>] ? call_softirq+0x1c/0x30 [<ffffffff8100de05>] ? do_softirq+0x65/0xa0 [<ffffffff81076d95>] ? irq_exit+0x85/0x90 [<ffffffff81516d80>] ? smp_apic_timer_interrupt+0x70/0x9b [<ffffffff8100bb93>] ? apic_timer_interrupt+0x13/0x20 To avoid the issue let's change the second check to test whether serio is NULL or not. Also, let's take i8042_lock in i8042_start() and i8042_stop() instead of trying to be overly smart and using memory barriers. Signed-off-by: Chen Hong <chenhong3@huawei.com> [dtor: take lock in i8042_start()/i8042_stop()] Cc: stable@vger.kernel.org Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.