Re: [PATCH] qla2xxx: Avoid triggering undefined behavior in qla2x00_mbx_completion()

[Laurence Oberman <loberman@redhat.com>]

On Thu, 2018-01-25 at 08:24 -0800, Bart Van Assche wrote:
> A left shift must shift less than the bit width of the left argument.
> Avoid triggering undefined behavior if ha->mbx_count == 32.
> 
> This patch avoids that UBSAN reports the following complaint:
> 
> UBSAN: Undefined behaviour in drivers/scsi/qla2xxx/qla_isr.c:275:14
> shift exponent 32 is too large for 32-bit type 'int'
> Call Trace:
>  dump_stack+0x4e/0x6c
>  ubsan_epilogue+0xd/0x3b
>  __ubsan_handle_shift_out_of_bounds+0x112/0x14c
>  qla2x00_mbx_completion+0x1c5/0x25d [qla2xxx]
>  qla2300_intr_handler+0x1ea/0x3bb [qla2xxx]
>  qla2x00_mailbox_command+0x77b/0x139a [qla2xxx]
>  qla2x00_mbx_reg_test+0x83/0x114 [qla2xxx]
>  qla2x00_chip_diag+0x354/0x45f [qla2xxx]
>  qla2x00_initialize_adapter+0x2c2/0xa4e [qla2xxx]
>  qla2x00_probe_one+0x1681/0x392e [qla2xxx]
>  pci_device_probe+0x10b/0x1f1
>  driver_probe_device+0x21f/0x3a4
>  __driver_attach+0xa9/0xe1
>  bus_for_each_dev+0x6e/0xb5
>  driver_attach+0x22/0x3c
>  bus_add_driver+0x1d1/0x2ae
>  driver_register+0x78/0x130
>  __pci_register_driver+0x75/0xa8
>  qla2x00_module_init+0x21b/0x267 [qla2xxx]
>  do_one_initcall+0x5a/0x1e2
>  do_init_module+0x9d/0x285
>  load_module+0x20db/0x38e3
>  SYSC_finit_module+0xa8/0xbc
>  SyS_finit_module+0x9/0xb
>  do_syscall_64+0x77/0x271
>  entry_SYSCALL64_slow_path+0x25/0x25
> 
> Reported-by: Meelis Roos <mroos@linux.ee>
> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> Cc: Himanshu Madhani <himanshu.madhani@cavium.com>
> ---
>  drivers/scsi/qla2xxx/qla_isr.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/qla2xxx/qla_isr.c
> b/drivers/scsi/qla2xxx/qla_isr.c
> index 16c43bd9bb83..79f538448364 100644
> --- a/drivers/scsi/qla2xxx/qla_isr.c
> +++ b/drivers/scsi/qla2xxx/qla_isr.c
> @@ -272,7 +272,8 @@ qla2x00_mbx_completion(scsi_qla_host_t *vha,
> uint16_t mb0)
>  	struct device_reg_2xxx __iomem *reg = &ha->iobase->isp;
>  
>  	/* Read all mbox registers? */
> -	mboxes = (1 << ha->mbx_count) - 1;
> +	WARN_ON_ONCE(ha->mbx_count > 32);
> +	mboxes = (1ULL << ha->mbx_count) - 1;
>  	if (!ha->mcp)
>  		ql_dbg(ql_dbg_async, vha, 0x5001, "MBX pointer
> ERROR.\n");
>  	else
> @@ -2884,7 +2885,8 @@ qla24xx_mbx_completion(scsi_qla_host_t *vha,
> uint16_t mb0)
>  	struct device_reg_24xx __iomem *reg = &ha->iobase->isp24;
>  
>  	/* Read all mbox registers? */
> -	mboxes = (1 << ha->mbx_count) - 1;
> +	WARN_ON_ONCE(ha->mbx_count > 32);
> +	mboxes = (1ULL << ha->mbx_count) - 1;
>  	if (!ha->mcp)
>  		ql_dbg(ql_dbg_async, vha, 0x504e, "MBX pointer
> ERROR.\n");
>  	else

This looks fine to me and I tested the earlier patch suggestion
supplied by Meelis.

Reviewed-by: Laurence Oberman <loberman@redhat.com>