[SRU][J][PATCH 1/1] bnxt_en: Fix memory corruption when FW resources change during ifdown

[Cengiz Can]

From: Sreekanth Reddy <sreekanth.reddy at broadcom.com>

bnxt_set_dflt_rings() assumes that it is always called before any TC has
been created.  So it doesn't take bp->num_tc into account and assumes
that it is always 0 or 1.

In the FW resource or capability change scenario, the FW will return
flags in bnxt_hwrm_if_change() that will cause the driver to
reinitialize and call bnxt_cancel_reservations().  This will lead to
bnxt_init_dflt_ring_mode() calling bnxt_set_dflt_rings() and bp->num_tc
may be greater than 1.  This will cause bp->tx_ring[] to be sized too
small and cause memory corruption in bnxt_alloc_cp_rings().

Fix it by properly scaling the TX rings by bp->num_tc in the code
paths mentioned above.  Add 2 helper functions to determine
bp->tx_nr_rings and bp->tx_nr_rings_per_tc.

Fixes: ec5d31e3c15d ("bnxt_en: Handle firmware reset status during IF_UP.")
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil at broadcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek at broadcom.com>
Signed-off-by: Sreekanth Reddy <sreekanth.reddy at broadcom.com>
Signed-off-by: Michael Chan <michael.chan at broadcom.com>
Link: https://patch.msgid.link/20250825175927.459987-2-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
(backported from commit 2747328ba2714f1a7454208dbbc1dc0631990b4a)
[bot_kybele: This tree has no bp->num_tc field, so the two helpers use
 netdev_get_num_tc(bp->dev) (the TC-count analogue used elsewhere, e.g.
 bnxt_reserve_rings) instead of bp->num_tc; also dropped the unrelated
 bnxt_cfg_one_usr_fltr/bnxt_cfg_usr_fltrs/bnxt_set_xps_mapping functions that
 git am spuriously pulled into the conflict block since they belong to other
 commits and don't exist here.]
CVE-2025-39810
Assisted-by: kybele:claude-opus-4.8
Signed-off-by: Cengiz Can <cengiz.can at canonical.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 24 ++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 0b435bd3db9d..e650c85145b3 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -10218,6 +10218,20 @@ static int bnxt_reinit_after_abort(struct bnxt *bp)
 	return rc;
 }
 
+static int bnxt_tx_nr_rings(struct bnxt *bp)
+{
+	int tcs = netdev_get_num_tc(bp->dev);
+
+	return tcs ? bp->tx_nr_rings_per_tc * tcs : bp->tx_nr_rings_per_tc;
+}
+
+static int bnxt_tx_nr_rings_per_tc(struct bnxt *bp)
+{
+	int tcs = netdev_get_num_tc(bp->dev);
+
+	return tcs ? bp->tx_nr_rings / tcs : bp->tx_nr_rings;
+}
+
 static int __bnxt_open_nic(struct bnxt *bp, bool irq_re_init, bool link_re_init)
 {
 	int rc = 0;
@@ -13062,7 +13076,7 @@ static void bnxt_trim_dflt_sh_rings(struct bnxt *bp)
 	bp->cp_nr_rings = min_t(int, bp->tx_nr_rings_per_tc, bp->rx_nr_rings);
 	bp->rx_nr_rings = bp->cp_nr_rings;
 	bp->tx_nr_rings_per_tc = bp->cp_nr_rings;
-	bp->tx_nr_rings = bp->tx_nr_rings_per_tc;
+	bp->tx_nr_rings = bnxt_tx_nr_rings(bp);
 }
 
 static int bnxt_set_dflt_rings(struct bnxt *bp, bool sh)
@@ -13093,12 +13107,12 @@ static int bnxt_set_dflt_rings(struct bnxt *bp, bool sh)
 		bnxt_trim_dflt_sh_rings(bp);
 	else
 		bp->cp_nr_rings = bp->tx_nr_rings_per_tc + bp->rx_nr_rings;
-	bp->tx_nr_rings = bp->tx_nr_rings_per_tc;
+	bp->tx_nr_rings = bnxt_tx_nr_rings(bp);
 
 	rc = __bnxt_reserve_rings(bp);
 	if (rc)
 		netdev_warn(bp->dev, "Unable to reserve tx rings\n");
-	bp->tx_nr_rings_per_tc = bp->tx_nr_rings;
+	bp->tx_nr_rings_per_tc = bnxt_tx_nr_rings_per_tc(bp);
 	if (sh)
 		bnxt_trim_dflt_sh_rings(bp);
 
@@ -13107,7 +13121,7 @@ static int bnxt_set_dflt_rings(struct bnxt *bp, bool sh)
 		rc = __bnxt_reserve_rings(bp);
 		if (rc)
 			netdev_warn(bp->dev, "2nd rings reservation failed.\n");
-		bp->tx_nr_rings_per_tc = bp->tx_nr_rings;
+		bp->tx_nr_rings_per_tc = bnxt_tx_nr_rings_per_tc(bp);
 	}
 	if (BNXT_CHIP_TYPE_NITRO_A0(bp)) {
 		bp->rx_nr_rings++;
@@ -13138,7 +13152,7 @@ static int bnxt_init_dflt_ring_mode(struct bnxt *bp)
 	if (rc)
 		goto init_dflt_ring_err;
 
-	bp->tx_nr_rings_per_tc = bp->tx_nr_rings;
+	bp->tx_nr_rings_per_tc = bnxt_tx_nr_rings_per_tc(bp);
 
 	bnxt_set_dflt_rfs(bp);
 
-- 
2.53.0