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SubjectRe: Another UBSAN warning from aic7xxx
> Fixing this reveals another UBSAN warning from the same driver, will fix 
> that too.

This is the warning - devinfo->target_offset is unsigned but
ahc_reset_channel() calls it with signed -1 for the parameter.

The patch below silences it but is it a good way?

[ 0.394215] ================================================================================
[ 0.394405] UBSAN: Undefined behaviour in drivers/scsi/aic7xxx/aic7xxx_core.c:2833:32
[ 0.394593] shift exponent -1 is negative
[ 0.394712] CPU: 0 PID: 1 Comm: swapper Not tainted 4.14.0-rc1-00009-g0666f560b71b-dirty #80
[ 0.394900] Hardware name: IBM -[867313X]-/-[M51SL]-, BIOS -[PLE168AUS-1.68]- 06/25/04
[ 0.395086] Call Trace:
[ 0.395214] dump_stack+0x16/0x18
[ 0.395335] ubsan_epilogue+0xe/0x2f
[ 0.395455] __ubsan_handle_shift_out_of_bounds+0xef/0x131
[ 0.395577] ? vprintk_emit+0x251/0x39c
[ 0.395694] ? vprintk_default+0x32/0x34
[ 0.395815] ahc_compile_devinfo+0x92/0xb8
[ 0.395933] ahc_reset_channel+0x5a/0x2c3
[ 0.396005] ? __alloc_workqueue_key+0x222/0x537
[ 0.396005] ahc_linux_initialize_scsi_bus+0x44/0x298
[ 0.396005] ? vsnprintf+0x3a0/0x629
[ 0.396005] ahc_linux_register_host+0x1a3/0x2b3
[ 0.396005] ahc_linux_pci_dev_probe+0x179/0x36e
[ 0.396005] ? kernfs_add_one+0x10c/0x1d5
[ 0.396005] pci_device_probe+0xaa/0x163
[ 0.396005] driver_probe_device+0x1c9/0x34c
[ 0.396005] __driver_attach+0x87/0xba
[ 0.396005] ? driver_probe_device+0x34c/0x34c
[ 0.396005] bus_for_each_dev+0x48/0x89
[ 0.396005] driver_attach+0x1d/0x33
[ 0.396005] ? driver_probe_device+0x34c/0x34c
[ 0.396005] bus_add_driver+0x184/0x275
[ 0.396005] driver_register+0x66/0x115
[ 0.396005] __pci_register_driver+0x44/0x6e
[ 0.396005] ahc_linux_pci_init+0x14/0x16
[ 0.396005] ahc_linux_init+0x87/0x95
[ 0.396005] ? spi_transport_init+0x1a4/0x1a4
[ 0.396005] do_one_initcall+0x4f/0x1da
[ 0.396005] ? next_arg+0xee/0x1e2
[ 0.396005] ? parameq+0x12/0xab
[ 0.396005] ? parse_args+0x177/0x390
[ 0.396005] kernel_init_freeable+0x1c4/0x247
[ 0.396005] ? rest_init+0x70/0x70
[ 0.396005] kernel_init+0xc/0x107
[ 0.396005] ? schedule_tail_wrapper+0x9/0xc
[ 0.396005] ? rest_init+0x70/0x70
[ 0.396005] ret_from_fork+0x19/0x24
[ 0.396005] ================================================================================


diff --git a/drivers/scsi/aic7xxx/aic7xxx_core.c b/drivers/scsi/aic7xxx/aic7xxx_core.c
index 381846164003..7c692336c18d 100644
--- a/drivers/scsi/aic7xxx/aic7xxx_core.c
+++ b/drivers/scsi/aic7xxx/aic7xxx_core.c
@@ -2828,7 +2828,11 @@ ahc_compile_devinfo(struct ahc_devinfo *devinfo, u_int our_id, u_int target,
devinfo->role = role;
if (channel == 'B')
devinfo->target_offset += 8;
- devinfo->target_mask = (0x01 << devinfo->target_offset);
+ if (target < AHC_NUM_TARGETS + 8) {
+ devinfo->target_mask = (0x01 << devinfo->target_offset);
+ } else {
+ devinfo->target_mask = 0;
+ }
}

void
--
Meelis Roos (mroos@linux.ee)

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