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List:       linux-driver-devel
Subject:    Re: [PATCH v2] staging: unisys: visorbus: fix kernel BUG discovered by day0 testing
From:       Greg KH <gregkh () linuxfoundation ! org>
Date:       2017-03-31 17:04:20
Message-ID: 20170331170420.GB27268 () kroah ! com
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On Fri, Mar 31, 2017 at 10:56:28AM -0400, David Kershner wrote:
> Fixes: 5b6f9b95f7ae ("staging: unisys: visorbus: get rid of create_bus_type.")
> 
> Kernel day0 testing robot reported a kernel BUG at drivers/base/driver.c!
> with the following call stack:
> 
> [   14.963563] ------------[ cut here ]------------
> [   14.967298] kernel BUG at drivers/base/driver.c:153!
> [   14.970948] invalid opcode: 0000 [#1] SMP
> [   14.974013] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc4-00790-g0789e2c \
> #1 [   14.978221] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS \
> 1.9.3-20161025_171302-gandalf 04/01/2014 [   14.983417] task: ffff88001ea46040 \
> task.stack: ffffc90000008000 [   14.987315] RIP: 0010:driver_register+0xa1/0xd0
> [   14.990044] RSP: 0000:ffffc9000000be60 EFLAGS: 00010246
> [   14.993039] RAX: 0000000000000000 RBX: ffffffff831d4c20 RCX: 0000000000000000
> [   14.997040] RDX: 000000000000004d RSI: ffffffff831d47c0 RDI: ffffffff831d4c20
> [   15.001511] RBP: ffffc9000000be78 R08: ffffc9000000be78 R09: ffffc9000000be7c
> [   15.006163] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
> [   15.010068] R13: 00000000ffffffff R14: ffffffff832f3923 R15: 0000000000000000
> [   15.013715] FS:  0000000000000000(0000) GS:ffff88001fa00000(0000) \
> knlGS:0000000000000000 [   15.017460] CS:  0010 DS: 0000 ES: 0000 CR0: \
> 0000000080050033 [   15.021268] CR2: 0000000000000000 CR3: 0000000003009000 CR4: \
> 00000000000006b0 [   15.025633] Call Trace:
> [   15.028069]  ? visorbus_register_visor_driver+0x3f/0x60
> [   15.031065]  ? init_unisys+0x3a/0x90
> [   15.033562]  ? device_resume_response+0x50/0x50
> [   15.036083]  visorinput_init+0x10/0x20
> [   15.038937]  do_one_initcall+0x9a/0x164
> [   15.041838]  ? set_debug_rodata+0x12/0x12
> [   15.045333]  kernel_init_freeable+0x11e/0x1a1
> [   15.048369]  ? rest_init+0x80/0x80
> [   15.050813]  kernel_init+0x9/0x100
> [   15.053353]  ret_from_fork+0x2c/0x40
> [   15.056009] Code: ff 85 c0 41 89 c4 75 13 48 8b 7b 70 31 f6 e8 97 16 be ff 44 89 \
> e0 5b 41 5c 5d c3 48 89 df e8 57 e1 ff ff 44 89 e0 5b 41 5c 5d c3 <0f> 0b 48 8b 33 \
> 48 c7 c7 a0 dd d5 82 e8 ec f0 6f ff 48 8b 73 08 [   15.065144] RIP: \
> driver_register+0xa1/0xd0 RSP: ffffc9000000be60 [   15.068360] ---[ end trace \
> 7d13369c38d80a8f ]--- 
> This bug will occur if the visorbus driver is built-in to the kernel, and
> the resulting kernel is run in an environment where visorbus devices are
> NOT supported, and an attempt is made to load any of the drivers: visorhba,
> visornic, or visorinput.
> 
> Checked to see if we have called bus_register, if not do not call
> driver_register.
> 
> Signed-off-by: David Kershner <david.kershner@unisys.com>
> Reviewed-by: Tim Sell <timothy.sell@unisys.com>
> ---
> - Changes from v1 - Made changes suggested by GregKH. Instead of reverting
> patch, just added the check for initialization.
> drivers/staging/unisys/visorbus/visorbus_main.c | 6 ++++++
> 1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/staging/unisys/visorbus/visorbus_main.c \
> b/drivers/staging/unisys/visorbus/visorbus_main.c index 4348072..9490977 100644
> --- a/drivers/staging/unisys/visorbus/visorbus_main.c
> +++ b/drivers/staging/unisys/visorbus/visorbus_main.c
> @@ -29,6 +29,7 @@
> #define CURRENT_FILE_PC VISOR_BUS_PC_visorbus_main_c
> #define POLLJIFFIES_NORMALCHANNEL 10
> 
> +static bool initialized; /* stores whether bus_registration was successful */
> static struct dentry *visorbus_debugfs_dir;
> 
> /*
> @@ -959,6 +960,9 @@ static void bus_device_info_init(
> */
> int visorbus_register_visor_driver(struct visor_driver *drv)
> {
> +	if (!initialized)
> +		return -ENODEV; /*can't register on a nonexistent bus*/

Same question about the lack of ' ' in your comment :(

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