[PATCH net] bnxt_en: Bound SW TPA IDs to prevent crashes

TPA IDs are generated by FW and can be up to 1024. bnxt_alloc_agg_idx is
intended to wrap the FW ID to a value in the range of [0, 255] and
generate a mapping between FW IDs and the wrapped software ID.

On a 57608 with firmware version 233, the firmware advertises 32
concurrent TPAs. As of the commit under fixes, bp->max_tpa on this NIC
is set to 32.

If the software ID from bnxt_alloc_agg_idx is above 31, this results in
an invalid address being loaded on this line:

  tpa_info = &rxr->rx_tpa[agg_id];

because rx_tpa is allocated with only bp->max_tpa (32) entries. Writes
to tpa_info later in the code are out of bounds.

This bug results in a crash at boot:

Oops: general protection fault, kernel NULL pointer dereference 0x8: 0000 [#1] SMP NOPTI
RIP: 0010:bnxt_rx_pkt+0xc0/0x1560
RSP: 0018:ffffc900009b8c78 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000048 RCX: 0000000206682516
RDX: ffffc900009b8db4 RSI: 0000000000000000 RDI: 01ffffff038fe1c0
RBP: ffffc9006e687480 R08: ffffc9006e687000 R09: 0000000000003048
R10: 0000000000000480 R11: ffff8881c6083900 R12: 0000000006682516
R13: ffff8881c6095400 R14: 0000000000000016 R15: ffff8881c6b66680
FS:  0000000000000000(0000) GS:ffff88fef3c77000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc8bda40584 CR3: 000000807c812001 CR4: 0000000008772ef0
PKRU: 55555554
Call Trace:
 <IRQ>
 ? __netif_receive_skb_list_core+0x1ca/0x250
 __bnxt_poll_work+0x152/0x280
 bnxt_poll_p5+0x1cd/0x480
 __napi_poll+0x30/0x180
 net_rx_action+0x20b/0x3b0
 ? note_gp_changes+0x53/0xe0
 ? tick_setup_sched_timer+0x180/0x180
 ? __napi_schedule+0x9a/0xb0
 ? bnxt_msix+0x24/0x30
 handle_softirqs+0xdd/0x2c0
 __irq_exit_rcu.llvm.3171231171502365008+0x47/0xf0
 common_interrupt+0x85/0x90
 </IRQ>
 <TASK>
 asm_common_interrupt+0x22/0x40

This stack trace is from a crash triggered when an out of bounds rx_tpa
is dereferenced. The invalid write mentioned above is silent in this
particular crash.

Fix this by adjusting bnxt_alloc_agg_idx so that any SW index greater
than or equal to bp->max_tpa goes through the collision logic and picks
the first available bit. Adjust the collision logic to only provide bits
within the range of [0, bp->max_tpa).

Fixes: 54c28fab2fa5 ("bnxt_en: Set bp->max_tpa according to what the FW supports")
Cc: [email protected]
Signed-off-by: Joe Damato <[email protected]>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index d3cb25abb632..f348fb93047d 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -1517,14 +1517,15 @@ static int bnxt_discard_rx(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
 	return 0;
 }
 
-static u16 bnxt_alloc_agg_idx(struct bnxt_rx_ring_info *rxr, u16 agg_id)
+static u16 bnxt_alloc_agg_idx(struct bnxt *bp, struct bnxt_rx_ring_info *rxr,
+			      u16 agg_id)
 {
 	struct bnxt_tpa_idx_map *map = rxr->rx_tpa_idx_map;
 	u16 idx = agg_id & MAX_TPA_P5_MASK;
 
-	if (test_bit(idx, map->agg_idx_bmap)) {
-		idx = find_first_zero_bit(map->agg_idx_bmap, MAX_TPA_P5);
-		if (idx >= MAX_TPA_P5)
+	if (idx >= bp->max_tpa || test_bit(idx, map->agg_idx_bmap)) {
+		idx = find_first_zero_bit(map->agg_idx_bmap, bp->max_tpa);
+		if (idx >= bp->max_tpa)
 			return INVALID_HW_RING_ID;
 	}
 	__set_bit(idx, map->agg_idx_bmap);
@@ -1589,7 +1590,7 @@ static void bnxt_tpa_start(struct bnxt *bp, struct bnxt_rx_ring_info *rxr,
 
 	if (bp->flags & BNXT_FLAG_CHIP_P5_PLUS) {
 		agg_id = TPA_START_AGG_ID_P5(tpa_start);
-		agg_id = bnxt_alloc_agg_idx(rxr, agg_id);
+		agg_id = bnxt_alloc_agg_idx(bp, rxr, agg_id);
 		if (unlikely(agg_id == INVALID_HW_RING_ID)) {
 			netdev_warn(bp->dev, "Unable to allocate agg ID for ring %d, agg 0x%x\n",
 				    rxr->bnapi->index,

base-commit: 4e15e89faac9f308baeb01f46c13a051814d2449
-- 
2.53.0-Meta