[PATCH] mpt3sas: Avoid test/set_bit() operating in non-allocated memory

[Breno Leitao]

There is a potential out-of-bounds access when using test_bit() on a
single word. The test_bit() and set_bit() functions operate on long
values, and when testing or setting a single word, they can exceed the
word boundary. KASAN detects this issue and produces a dump:

	 BUG: KASAN: slab-out-of-bounds in _scsih_add_device.constprop.0 (./arch/x86/include/asm/bitops.h:60 ./include/asm-generic/bitops/instrumented-atomic.h:29 drivers/scsi/mpt3sas/mpt3sas_scsih.c:7331) mpt3sas

	 Write of size 8 at addr ffff8881d26e3c60 by task kworker/u1536:2/2965

For full log, please look at [1].

Make the allocation at least the size of sizeof(unsigned long) so that
set_bit() and test_bit() have sufficient room for read/write operations
without overwriting unallocated memory.

[1] Link: https://lore.kernel.org/all/ZkNcALr3W3KGYYJG@xxxxxxxxx/

Suggested-by: Keith Busch <kbusch@xxxxxxxxxx>
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
---
 drivers/scsi/mpt3sas/mpt3sas_base.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
index 258647fc6bdd..fe9f4a4175d1 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -8512,6 +8512,12 @@ mpt3sas_base_attach(struct MPT3SAS_ADAPTER *ioc)
 	ioc->pd_handles_sz = (ioc->facts.MaxDevHandle / 8);
 	if (ioc->facts.MaxDevHandle % 8)
 		ioc->pd_handles_sz++;
+	/* pd_handles_sz should have, at least, the minimal room
+	 * for set_bit()/test_bit(), otherwise out-of-memory touch
+	 * may occur
+	 */
+	ioc->pd_handles_sz = ALIGN(ioc->pd_handles_sz, sizeof(unsigned long));
+
 	ioc->pd_handles = kzalloc(ioc->pd_handles_sz,
 	    GFP_KERNEL);
 	if (!ioc->pd_handles) {
@@ -8529,6 +8535,12 @@ mpt3sas_base_attach(struct MPT3SAS_ADAPTER *ioc)
 	ioc->pend_os_device_add_sz = (ioc->facts.MaxDevHandle / 8);
 	if (ioc->facts.MaxDevHandle % 8)
 		ioc->pend_os_device_add_sz++;
+
+	/* pend_os_device_add_sz should have, at least, the minimal room
+	 * for set_bit()/test_bit(), otherwise out-of-memory may occur
+	 */
+	ioc->pend_os_device_add_sz = ALIGN(ioc->pend_os_device_add_sz,
+					   sizeof(unsigned long));
 	ioc->pend_os_device_add = kzalloc(ioc->pend_os_device_add_sz,
 	    GFP_KERNEL);
 	if (!ioc->pend_os_device_add) {
-- 
2.43.0