[PATCH v4] scsi: mvumi: reject handshake sizes that overflow the list allocations

[Yehyeong Lee]

mvumi_hs_process_page() takes max_io, the two command entry sizes and the
list depth from the firmware handshake page.  The entry sizes are u8 fields
used as shift counts, and 1 is an int, so a count of 29 or more makes the
<< 2 applied to the shift overflow an int; a count of 32 or more is
undefined outright.  max_io is a u16, and the sizes derived from the shifts
are multiplied by it in mvumi_init_data() to size three unsigned int
allocations, so a large entry size wraps the product and the loops that
follow then walk and write past the short allocation.  The list depth is
used as a shift count too, but only when the firmware sets
HS_CAPABILITY_NEW_PAGE_IO_DEPTH_DEF; a count of 32 or more is undefined
there as well.  The depth also sets how many entries the inbound and
outbound rings hold, and the per-command slot index wraps on that count
while the rings are allocated for max_io entries, so a depth yielding more
entries than max_io -- or none -- walks the index past them.
max_devices_support sizes the target_map bitmap in the same allocation.  A
host reset runs the handshake again, but mvumi_init_data() returns early
once MVUMI_FW_ALLOC is set, so the buffers keep the sizes they were
allocated with while the newly reported values drive the indexing:
mvumi_flush_cache() then reads target_map past its end and
mvumi_sdev_configure() sets a bit past it.  The handshake is retried as
well, because mvumi_handshake_event() discards the error, so a page that
was already rejected can be presented again.

Reject an entry size above 29, which keeps 1U << n and the shift that
follows it inside an unsigned int.  Then compute the worst-case allocation
size in u64 at the top of mvumi_init_data() and reject it if it does not
fit an unsigned int.  That total bounds all three allocations: the inbound
list total, the outbound data pool and the tag arrays, whose sizes are the
same products plus smaller terms.  Reject a list depth of 32 or more on the
shifted path so the shift stays defined, and reject a resulting entry count
that is zero or above max_io so the slot index cannot walk past the rings.
The shifts also use 1U now so that a legal count cannot overflow an int.
Take the page's values into locals and run every check on those.  Once
MVUMI_FW_ALLOC is set the buffers already exist, so only check that no
reported size, max_devices_support included, is larger than the one its
buffer was allocated for, and leave the size fields alone: they already
hold the sizes those buffers have.  Only the first handshake, whose values
size the allocations, assigns them.

No realistic controller is rejected: a controller reporting 4096 commands
with 64 KiB entries and a depth of 12 needs 513 MiB and passes unchanged.

Fixes: f0c568a478f0 ("[SCSI] mvumi: Add Marvell UMI driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Yehyeong Lee <yhlee@xxxxxxxxxxxxxxxxxx>
---
v4:
- a reset does not reallocate, so validate the reported sizes against the
  current ones and leave the size fields unchanged; only the first handshake
  assigns them.  This also means a page the driver has already rejected
  cannot be presented again to get past the check, which the retry in
  mvumi_handshake_event() allows (Sashiko).
- include max_devices_support in that check; it sizes target_map, which
  mvumi_flush_cache() reads and mvumi_sdev_configure() writes (Sashiko).

v3:
- reject a reset handshake whose sizes exceed the existing allocation,
  which is not reallocated on reset (Sashiko).

v2:
- compute the allocation total in u64 so the check also holds on 32-bit
  (Sashiko).
- reject a handshake list depth whose entry count exceeds max_io, which
  would walk the per-command ring past its allocation (Sashiko).

 drivers/scsi/mvumi.c | 87 ++++++++++++++++++++++++++++++++++++++------
 1 file changed, 75 insertions(+), 12 deletions(-)

diff --git a/drivers/scsi/mvumi.c b/drivers/scsi/mvumi.c
index e70d336b4ab39..4fc0cf819c271 100644
--- a/drivers/scsi/mvumi.c
+++ b/drivers/scsi/mvumi.c
@@ -912,10 +912,23 @@ static int mvumi_init_data(struct mvumi_hba *mhba)
 	unsigned int tmp_size, offset, i;
 	void *virmem, *v;
 	dma_addr_t p;
+	u64 total;
 
 	if (mhba->fw_flag & MVUMI_FW_ALLOC)
 		return 0;
 
+	/* These are firmware-supplied and size the allocations below. */
+	total = (u64)mhba->ib_max_size * mhba->max_io +
+		(u64)mhba->ob_max_size * mhba->max_io +
+		sizeof(struct mvumi_dyn_list_entry) * (u64)mhba->max_io +
+		160;
+	if (total > UINT_MAX) {
+		dev_err(&mhba->pdev->dev,
+			"handshake sizes too large: io %u, in %u, out %u\n",
+			mhba->max_io, mhba->ib_max_size, mhba->ob_max_size);
+		return -1;
+	}
+
 	tmp_size = mhba->ib_max_size * mhba->max_io;
 	if (mhba->hba_capability & HS_CAPABILITY_SUPPORT_DYN_SRC)
 		tmp_size += sizeof(struct mvumi_dyn_list_entry) * mhba->max_io;
@@ -1048,30 +1061,80 @@ static int mvumi_hs_process_page(struct mvumi_hba *mhba,
 	}
 
 	switch (hs_header->page_code) {
-	case HS_PAGE_FIRM_CAP:
+	case HS_PAGE_FIRM_CAP: {
+		unsigned int new_max_io, new_ib_max_size, new_ob_max_size;
+		unsigned int new_list_num_io;
+		unsigned short new_max_target_id, new_capability;
+
 		hs_page1 = (struct mvumi_hs_page1 *) hs_header;
 
-		mhba->max_io = hs_page1->max_io_support;
-		mhba->list_num_io = hs_page1->cl_inout_list_depth;
-		mhba->max_transfer_size = hs_page1->max_transfer_size;
-		mhba->max_target_id = hs_page1->max_devices_support;
-		mhba->hba_capability = hs_page1->capability;
-		mhba->ib_max_size_setting = hs_page1->cl_in_max_entry_size;
-		mhba->ib_max_size = (1 << hs_page1->cl_in_max_entry_size) << 2;
+		/* Firmware-supplied shift counts: (1U << n) << 2 must fit. */
+		if (hs_page1->cl_in_max_entry_size > 29 ||
+		    hs_page1->cl_out_max_entry_size > 29) {
+			dev_err(&mhba->pdev->dev,
+				"invalid handshake entry size\n");
+			return -1;
+		}
 
-		mhba->ob_max_size_setting = hs_page1->cl_out_max_entry_size;
-		mhba->ob_max_size = (1 << hs_page1->cl_out_max_entry_size) << 2;
+		new_max_io = hs_page1->max_io_support;
+		new_ib_max_size = (1U << hs_page1->cl_in_max_entry_size) << 2;
+		new_ob_max_size = (1U << hs_page1->cl_out_max_entry_size) << 2;
+		new_max_target_id = hs_page1->max_devices_support;
+		new_capability = hs_page1->capability;
+
+		new_list_num_io = hs_page1->cl_inout_list_depth;
+		if (new_capability & HS_CAPABILITY_NEW_PAGE_IO_DEPTH_DEF) {
+			if (hs_page1->cl_inout_list_depth >= 32) {
+				dev_err(&mhba->pdev->dev,
+					"invalid handshake list depth\n");
+				return -1;
+			}
+			new_list_num_io = 1U << hs_page1->cl_inout_list_depth;
+		}
+		/* The rings hold max_io entries but the index wraps on list_num_io. */
+		if (new_list_num_io == 0 || new_list_num_io > new_max_io) {
+			dev_err(&mhba->pdev->dev,
+				"invalid handshake list depth: %u entries for %u commands\n",
+				new_list_num_io, new_max_io);
+			return -1;
+		}
 
 		dev_dbg(&mhba->pdev->dev, "FW version:%d\n",
 						hs_page1->fw_ver.ver_build);
 
+		/* A host reset does not reallocate, so the sizes have to stay
+		 * the ones the buffers were allocated with.  Only check that
+		 * the firmware is not asking for more than they hold.
+		 */
+		if (mhba->fw_flag & MVUMI_FW_ALLOC) {
+			if (new_max_io > mhba->max_io ||
+			    new_ib_max_size > mhba->ib_max_size ||
+			    new_ob_max_size > mhba->ob_max_size ||
+			    new_list_num_io > mhba->list_num_io ||
+			    new_max_target_id > mhba->max_target_id) {
+				dev_err(&mhba->pdev->dev,
+					"handshake sizes grew across reset\n");
+				return -1;
+			}
+			break;
+		}
+
+		mhba->max_io = new_max_io;
+		mhba->list_num_io = new_list_num_io;
+		mhba->max_transfer_size = hs_page1->max_transfer_size;
+		mhba->max_target_id = new_max_target_id;
+		mhba->hba_capability = new_capability;
+		mhba->ib_max_size_setting = hs_page1->cl_in_max_entry_size;
+		mhba->ib_max_size = new_ib_max_size;
+		mhba->ob_max_size_setting = hs_page1->cl_out_max_entry_size;
+		mhba->ob_max_size = new_ob_max_size;
+
 		if (mhba->hba_capability & HS_CAPABILITY_SUPPORT_COMPACT_SG)
 			mhba->eot_flag = 22;
 		else
 			mhba->eot_flag = 27;
-		if (mhba->hba_capability & HS_CAPABILITY_NEW_PAGE_IO_DEPTH_DEF)
-			mhba->list_num_io = 1 << hs_page1->cl_inout_list_depth;
 		break;
+	}
 	default:
 		dev_err(&mhba->pdev->dev, "handshake: page code error\n");
 		return -1;

base-commit: 24a19b953e2a3d0ea5a8c4951a0ab8f32720c907
-- 
2.43.0