[PATCH net v2] dpaa2-switch: validate num_ifs to prevent out-of-bounds write

[Junrui Luo]

The driver obtains sw_attr.num_ifs from firmware via dpsw_get_attributes()
but never validates it against DPSW_MAX_IF (64). This value controls
iteration in dpaa2_switch_fdb_get_flood_cfg(), which writes port indices
into the fixed-size cfg->if_id[DPSW_MAX_IF] array. When firmware reports
num_ifs >= 64, the loop can write past the array bounds.

Add a bound check for num_ifs in dpaa2_switch_init().

dpaa2_switch_fdb_get_flood_cfg() appends the control interface (port
num_ifs) after all matched ports. When num_ifs == DPSW_MAX_IF and all
ports match the flood filter, the loop fills all 64 slots and the control
interface write overflows by one entry.

The check uses >= because num_ifs == DPSW_MAX_IF is also functionally
broken.

build_if_id_bitmap() silently drops any ID >= 64:
      if (id[i] < DPSW_MAX_IF)
          bmap[id[i] / 64] |= ...

Fixes: 539dda3c5d19 ("staging: dpaa2-switch: properly setup switching domains")
Signed-off-by: Junrui Luo <moonafterrain@xxxxxxxxxxx>
---
Changes in v2:
- Drop self-referential Reported-by tags
- Update Fixes tag to reference 539dda3c5d19
- Expand the commit description
- Link to v1: https://lore.kernel.org/all/SYBPR01MB788110DFE66BA1A5CE7E594FAF6DA@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
---
 drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
index 66240c340492..78e21b46a5ba 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
@@ -3034,6 +3034,13 @@ static int dpaa2_switch_init(struct fsl_mc_device *sw_dev)
 		goto err_close;
 	}
 
+	if (ethsw->sw_attr.num_ifs >= DPSW_MAX_IF) {
+		dev_err(dev, "DPSW num_ifs %u exceeds max %u\n",
+			ethsw->sw_attr.num_ifs, DPSW_MAX_IF);
+		err = -EINVAL;
+		goto err_close;
+	}
+
 	err = dpsw_get_api_version(ethsw->mc_io, 0,
 				   &ethsw->major,
 				   &ethsw->minor);

---
base-commit: 9702969978695d9a699a1f34771580cdbb153b33
change-id: 20260224-fixes-a33979dd5060

Best regards,
-- 
Junrui Luo <moonafterrain@xxxxxxxxxxx>