[PATCH net v2] hv_netvsc: Stop PPI parsing on invalid metadata

[PATCH net v2] hv_netvsc: Stop PPI parsing on invalid metadata

[Erni Sri Satya Vennela]

rndis_get_ppi() uses continue when a per-packet information entry has an
invalid size or offset, or cannot hold the requested metadata. However,
the remaining length and entry pointer are only updated at the bottom
of the loop. Each error path therefore retries the same invalid entry
indefinitely, repeatedly logging the error and preventing receive
processing from completing.

Return NULL on these validation failures instead of continuing. This
terminates the lookup when malformed metadata is encountered while
preserving the existing behavior for valid entries.

The issue was reported through an internal bug-tracking system and
confirmed by manual code inspection. The pre-fix hang has not been
reproduced locally.

Fixes: 44144185951a ("hv_netvsc: Add validation for untrusted Hyper-V values")
Cc: stable@vger.kernel.org
Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Wei Liu <liuwe@microsoft.com>
---
Changes in v2:
* Add Cc: stable@vger.kernel.org
* Clarify how the issue was reported and confirmed in commit message.
---
 drivers/net/hyperv/rndis_filter.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index 9b6c44979b4e..2c30abf9faf8 100644
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -401,12 +401,12 @@ static inline void *rndis_get_ppi(struct net_device *ndev,
 		/* Validate ppi_offset and ppi_size */
 		if (ppi->size > len) {
 			netdev_err(ndev, "Invalid ppi size: %u\n", ppi->size);
-			continue;
+			return NULL;
 		}
 
 		if (ppi->ppi_offset >= ppi->size) {
 			netdev_err(ndev, "Invalid ppi_offset: %u\n", ppi->ppi_offset);
-			continue;
+			return NULL;
 		}
 
 		if (ppi->type == type && ppi->internal == internal) {
@@ -414,7 +414,7 @@ static inline void *rndis_get_ppi(struct net_device *ndev,
 			if (ppi->size - ppi->ppi_offset < ppi_size) {
 				netdev_err(ndev, "Invalid ppi: size %u ppi_offset %u\n",
 					   ppi->size, ppi->ppi_offset);
-				continue;
+				return NULL;
 			}
 			return (void *)((ulong)ppi + ppi->ppi_offset);
 		}

base-commit: f71ff7d406523748bfb8236830c7eaa6a308aaa1
-- 
2.34.1