xsk: Add overflow check for u64 division, stored into u32 (b16a87d0) · Commits · 戴 / test

The npgs member of struct xdp_umem is an u32 entity, and stores the number of pages the UMEM consumes. The calculation of npgs npgs = size / PAGE_SIZE can overflow. To avoid overflow scenarios, the division is now first stored in a u64, and the result is verified to fit into 32b. An alternative would be storing the npgs as a u64, however, this wastes memory and is an unrealisticly large packet area. Fixes: ("xsk: add user memory registration support sockopt") Reported-by:

"Minh Bùi Quang" <minhquangbui99@gmail.com> Signed-off-by:

Björn Töpel <bjorn.topel@intel.com> Signed-off-by:

Daniel Borkmann <daniel@iogearbox.net> Acked-by:

Jonathan Lemon <jonathan.lemon@gmail.com> Link: https://lore.kernel.org/bpf/CACtPs=GGvV-_Yj6rbpzTVnopgi5nhMoCcTkSkYrJHGQHJWFZMQ@mail.gmail.com/ Link: https://lore.kernel.org/bpf/20200525080400.13195-1-bjorn.topel@gmail.com

net/xdp/xdp_umem.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -341,8 +341,8 @@ static int xdp_umem_reg(struct xdp_umem umem, struct xdp_umem_reg mr)
		{
		bool unaligned_chunks = mr->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;
		u32 chunk_size = mr->chunk_size, headroom = mr->headroom;
		u64 npgs, addr = mr->addr, size = mr->len;
		unsigned int chunks, chunks_per_page;
		u64 addr = mr->addr, size = mr->len;
		int err;

		if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE \|\| chunk_size > PAGE_SIZE) {
		@@ -372,6 +372,10 @@ static int xdp_umem_reg(struct xdp_umem umem, struct xdp_umem_reg mr)
		if ((addr + size) < addr)
		return -EINVAL;

		npgs = div_u64(size, PAGE_SIZE);
		if (npgs > U32_MAX)
		return -EINVAL;

		chunks = (unsigned int)div_u64(size, chunk_size);
		if (chunks == 0)
		return -EINVAL;
		@@ -391,7 +395,7 @@ static int xdp_umem_reg(struct xdp_umem umem, struct xdp_umem_reg mr)
		umem->size = size;
		umem->headroom = headroom;
		umem->chunk_size_nohr = chunk_size - headroom;
		umem->npgs = size / PAGE_SIZE;
		umem->npgs = (u32)npgs;
		umem->pgs = NULL;
		umem->user = NULL;
		umem->flags = mr->flags;

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