[PATCH] net: mana: cap HWC init max message size to HW_CHANNEL_MAX_REQUEST_SIZE

[PATCH] net: mana: cap HWC init max message size to HW_CHANNEL_MAX_REQUEST_SIZE

[Michael Bommarito]

mana_hwc_init_event_handler() in hw_channel.c stores device-advertised
HWC_INIT_DATA_MAX_REQUEST and HWC_INIT_DATA_MAX_RESPONSE values
without bounds checking. mana_hwc_alloc_dma_buf() later computes the
DMA buffer size as MANA_PAGE_ALIGN(q_depth * max_msg_size) in 32-bit
arithmetic. A malicious device returning a large max_msg_size causes
the product to wrap, allocating a small buffer while laying out
q_depth request slots at the unwrapped stride, placing slots outside
the allocation.

Impact: a compromised hypervisor device model or malicious MANA PCI
device can cause out-of-bounds DMA buffer writes during HWC channel
initialization. A reproducer is available on request.

Clamp both values to HW_CHANNEL_MAX_REQUEST_SIZE (4096), consistent
with the cap already applied at the channel-create callsite.

Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
---
 drivers/net/ethernet/microsoft/mana/hw_channel.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c b/drivers/net/ethernet/microsoft/mana/hw_channel.c
index 48a9acea4ab6c..a0916b50cffce 100644
--- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
+++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
@@ -152,10 +152,14 @@ static void mana_hwc_init_event_handler(void *ctx, struct gdma_queue *q_self,
 			break;
 
 		case HWC_INIT_DATA_MAX_REQUEST:
+			if (val == 0 || val > HW_CHANNEL_MAX_REQUEST_SIZE)
+				val = HW_CHANNEL_MAX_REQUEST_SIZE;
 			hwc->hwc_init_max_req_msg_size = val;
 			break;
 
 		case HWC_INIT_DATA_MAX_RESPONSE:
+			if (val == 0 || val > HW_CHANNEL_MAX_REQUEST_SIZE)
+				val = HW_CHANNEL_MAX_REQUEST_SIZE;
 			hwc->hwc_init_max_resp_msg_size = val;
 			break;
 
-- 
2.53.0