[PATCH 6.19 176/220] net: mvpp2: guard flow control update with global_tx_fc in buffer switching

Greg Kroah-Hartman
2026-03-23T14:00:46Z

From: Muhammad Hammad Ijaz <mhijaz@amazon.com>

[ Upstream commit 8a63baadf08453f66eb582fdb6dd234f72024723 ]

mvpp2_bm_switch_buffers() unconditionally calls
mvpp2_bm_pool_update_priv_fc() when switching between per-cpu and
shared buffer pool modes. This function programs CM3 flow control
registers via mvpp2_cm3_read()/mvpp2_cm3_write(), which dereference
priv->cm3_base without any NULL check.

When the CM3 SRAM resource is not present in the device tree (the
third reg entry added by commit 60523583b07c ("dts: marvell: add CM3
SRAM memory to cp11x ethernet device tree")), priv->cm3_base remains
NULL and priv->global_tx_fc is false. Any operation that triggers
mvpp2_bm_switch_buffers(), for example an MTU change that crosses
the jumbo frame threshold, will crash:

Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000000
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
pc : readl+0x0/0x18
lr : mvpp2_cm3_read.isra.0+0x14/0x20
Call trace:
readl+0x0/0x18
mvpp2_bm_pool_update_fc+0x40/0x12c
mvpp2_bm_pool_update_priv_fc+0x94/0xd8
mvpp2_bm_switch_buffers.isra.0+0x80/0x1c0
mvpp2_change_mtu+0x140/0x380
__dev_set_mtu+0x1c/0x38
dev_set_mtu_ext+0x78/0x118
dev_set_mtu+0x48/0xa8
dev_ifsioc+0x21c/0x43c
dev_ioctl+0x2d8/0x42c
sock_ioctl+0x314/0x378

Every other flow control call site in the driver already guards
hardware access with either priv->global_tx_fc or port->tx_fc.
mvpp2_bm_switch_buffers() is the only place that omits this check.

Add the missing priv->global_tx_fc guard to both the disable and
re-enable calls in mvpp2_bm_switch_buffers(), consistent with the
rest of the driver.

Fixes: 3a616b92a9d1 ("net: mvpp2: Add TX flow control support for jumbo frames")
Signed-off-by: Muhammad Hammad Ijaz <mhijaz@amazon.com>
Reviewed-by: Gunnar Kudrjavets <gunnarku@amazon.com>
Link: https://patch.msgid.link/20260316193157.65748-1-mhijaz@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
index 33426fded919a..789e14bb1377a 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -5018,7 +5018,7 @@ static int mvpp2_bm_switch_buffers(struct mvpp2 *priv, bool percpu)
if (priv->percpu_pools)
numbufs = port->nrxqs * 2;

- if (change_percpu)
+ if (change_percpu && priv->global_tx_fc)
mvpp2_bm_pool_update_priv_fc(priv, false);

for (i = 0; i < numbufs; i++)
@@ -5043,7 +5043,7 @@ static int mvpp2_bm_switch_buffers(struct mvpp2 *priv, bool percpu)
mvpp2_open(port->dev);
}

- if (change_percpu)
+ if (change_percpu && priv->global_tx_fc)
mvpp2_bm_pool_update_priv_fc(priv, true);

return 0;
--
2.51.0