[PATCH] mpt3sas: Don't overreach ioc->reply_post[] during initialization

[Calvin Owens]

In _base_make_ioc_operational(), we walk ioc->reply_queue_list and pull
a pointer out of successive elements of ioc->reply_post[] for each entry
in that list if RDPQ is enabled.

Since the code pulls the pointer for the next iteration at the bottom of
the loop, it triggers the a KASAN dump on the final iteration:

    BUG: KASAN: slab-out-of-bounds in _base_make_ioc_operational+0x47b7/0x47e0 [mpt3sas] at addr ffff880754816ab0
    Read of size 8 by task modprobe/305
    <snip>
    Call Trace:
     [<ffffffff81dfc591>] dump_stack+0x4d/0x6c
     [<ffffffff814c9689>] print_trailer+0xf9/0x150
     [<ffffffff814ceda4>] object_err+0x34/0x40
     [<ffffffff814d1231>] kasan_report_error+0x221/0x530
     [<ffffffff814d1673>] __asan_report_load8_noabort+0x43/0x50
     [<ffffffffa0043637>] _base_make_ioc_operational+0x47b7/0x47e0 [mpt3sas]
     [<ffffffffa0049a51>] mpt3sas_base_attach+0x1991/0x2120 [mpt3sas]
     [<ffffffffa0053c93>] _scsih_probe+0xeb3/0x16b0 [mpt3sas]
     [<ffffffff81ebd047>] local_pci_probe+0xc7/0x170
     [<ffffffff81ebf2cf>] pci_device_probe+0x20f/0x290
     [<ffffffff820d50cd>] really_probe+0x17d/0x600
     [<ffffffff820d56a3>] __driver_attach+0x153/0x190
     [<ffffffff820cffac>] bus_for_each_dev+0x11c/0x1a0
     [<ffffffff820d421d>] driver_attach+0x3d/0x50
     [<ffffffff820d378a>] bus_add_driver+0x44a/0x5f0
     [<ffffffff820d666c>] driver_register+0x18c/0x3b0
     [<ffffffff81ebcb76>] __pci_register_driver+0x156/0x200
     [<ffffffffa00c8135>] _mpt3sas_init+0x135/0x1000 [mpt3sas]
     [<ffffffff81000423>] do_one_initcall+0x113/0x2b0
     [<ffffffff813caa5a>] do_init_module+0x1d0/0x4d8
     [<ffffffff81273909>] load_module+0x6729/0x8dc0
     [<ffffffff81276123>] SYSC_init_module+0x183/0x1a0
     [<ffffffff8127625e>] SyS_init_module+0xe/0x10
     [<ffffffff828fe7d7>] entry_SYSCALL_64_fastpath+0x12/0x6a

Fix this by pulling the value at the beginning of the loop.

Signed-off-by: Calvin Owens <calvinowens@xxxxxx>
---
 drivers/scsi/mpt3sas/mpt3sas_base.c | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
index e4db5fb..8c44b9c 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -5030,7 +5030,7 @@ _base_make_ioc_ready(struct MPT3SAS_ADAPTER *ioc, int sleep_flag,
 static int
 _base_make_ioc_operational(struct MPT3SAS_ADAPTER *ioc, int sleep_flag)
 {
-	int r, i;
+	int r, i, index;
 	unsigned long	flags;
 	u32 reply_address;
 	u16 smid;
@@ -5039,8 +5039,7 @@ _base_make_ioc_operational(struct MPT3SAS_ADAPTER *ioc, int sleep_flag)
 	struct _event_ack_list *delayed_event_ack, *delayed_event_ack_next;
 	u8 hide_flag;
 	struct adapter_reply_queue *reply_q;
-	long reply_post_free;
-	u32 reply_post_free_sz, index = 0;
+	Mpi2ReplyDescriptorsUnion_t *reply_post_free_contig;
 
 	dinitprintk(ioc, pr_info(MPT3SAS_FMT "%s\n", ioc->name,
 	    __func__));
@@ -5124,27 +5123,27 @@ _base_make_ioc_operational(struct MPT3SAS_ADAPTER *ioc, int sleep_flag)
 		_base_assign_reply_queues(ioc);
 
 	/* initialize Reply Post Free Queue */
-	reply_post_free_sz = ioc->reply_post_queue_depth *
-	    sizeof(Mpi2DefaultReplyDescriptor_t);
-	reply_post_free = (long)ioc->reply_post[index].reply_post_free;
+	index = 0;
+	reply_post_free_contig = ioc->reply_post[0].reply_post_free;
 	list_for_each_entry(reply_q, &ioc->reply_queue_list, list) {
+		/*
+		 * If RDPQ is enabled, switch to the next allocation.
+		 * Otherwise advance within the contiguous region.
+		 */
+		if (ioc->rdpq_array_enable) {
+			reply_q->reply_post_free =
+				ioc->reply_post[index++].reply_post_free;
+		} else {
+			reply_q->reply_post_free = reply_post_free_contig;
+			reply_post_free_contig += ioc->reply_post_queue_depth;
+		}
+
 		reply_q->reply_post_host_index = 0;
-		reply_q->reply_post_free = (Mpi2ReplyDescriptorsUnion_t *)
-		    reply_post_free;
 		for (i = 0; i < ioc->reply_post_queue_depth; i++)
 			reply_q->reply_post_free[i].Words =
 			    cpu_to_le64(ULLONG_MAX);
 		if (!_base_is_controller_msix_enabled(ioc))
 			goto skip_init_reply_post_free_queue;
-		/*
-		 * If RDPQ is enabled, switch to the next allocation.
-		 * Otherwise advance within the contiguous region.
-		 */
-		if (ioc->rdpq_array_enable)
-			reply_post_free = (long)
-			    ioc->reply_post[++index].reply_post_free;
-		else
-			reply_post_free += reply_post_free_sz;
 	}
  skip_init_reply_post_free_queue:
 
-- 
2.8.0.rc2