[PATCH bpf v3] xsk: Add missing overflow check in xdp_umem_reg

[Kal Conley]

The number of chunks can overflow u32. Make sure to return -EINVAL on
overflow.

Also remove a redundant u32 cast assigning umem->npgs.

Fixes: bbff2f321a86 ("xsk: new descriptor addressing scheme")
Signed-off-by: Kal Conley <kal.conley@xxxxxxxxxxx>
---
 net/xdp/xdp_umem.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index 4681e8e8ad94..02207e852d79 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -150,10 +150,11 @@ static int xdp_umem_account_pages(struct xdp_umem *umem)
 
 static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 {
-	u32 npgs_rem, chunk_size = mr->chunk_size, headroom = mr->headroom;
 	bool unaligned_chunks = mr->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;
-	u64 npgs, addr = mr->addr, size = mr->len;
-	unsigned int chunks, chunks_rem;
+	u32 chunk_size = mr->chunk_size, headroom = mr->headroom;
+	u64 addr = mr->addr, size = mr->len;
+	u32 chunks_rem, npgs_rem;
+	u64 chunks, npgs;
 	int err;
 
 	if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE || chunk_size > PAGE_SIZE) {
@@ -188,8 +189,8 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	if (npgs > U32_MAX)
 		return -EINVAL;
 
-	chunks = (unsigned int)div_u64_rem(size, chunk_size, &chunks_rem);
-	if (chunks == 0)
+	chunks = div_u64_rem(size, chunk_size, &chunks_rem);
+	if (!chunks || chunks > U32_MAX)
 		return -EINVAL;
 
 	if (!unaligned_chunks && chunks_rem)
@@ -202,7 +203,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	umem->headroom = headroom;
 	umem->chunk_size = chunk_size;
 	umem->chunks = chunks;
-	umem->npgs = (u32)npgs;
+	umem->npgs = npgs;
 	umem->pgs = NULL;
 	umem->user = NULL;
 	umem->flags = mr->flags;
-- 
2.39.2