From: Björn Töpel bjorn.topel@intel.com
[ Upstream commit 2b1667e54caf95e1e4249d9068eea7a3089a5229 ]
For AF_XDP sockets, there was a discrepancy between the number of of pinned pages and the size of the umem region.
The size of the umem region is used to validate the AF_XDP descriptor addresses. The logic that pinned the pages covered by the region only took whole pages into consideration, creating a mismatch between the size and pinned pages. A user could then pass AF_XDP addresses outside the range of pinned pages, but still within the size of the region, crashing the kernel.
This change correctly calculates the number of pages to be pinned. Further, the size check for the aligned mode is simplified. Now the code simply checks if the size is divisible by the chunk size.
Fixes: bbff2f321a86 ("xsk: new descriptor addressing scheme") Reported-by: Ciara Loftus ciara.loftus@intel.com Signed-off-by: Björn Töpel bjorn.topel@intel.com Signed-off-by: Alexei Starovoitov ast@kernel.org Tested-by: Ciara Loftus ciara.loftus@intel.com Acked-by: Song Liu songliubraving@fb.com Link: https://lore.kernel.org/bpf/20200910075609.7904-1-bjorn.topel@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/xdp/xdp_umem.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-)
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c index e97db37354e4f..b010bfde01490 100644 --- a/net/xdp/xdp_umem.c +++ b/net/xdp/xdp_umem.c @@ -303,10 +303,10 @@ 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; - u32 chunk_size = mr->chunk_size, headroom = mr->headroom; u64 npgs, addr = mr->addr, size = mr->len; - unsigned int chunks, chunks_per_page; + unsigned int chunks, chunks_rem; int err;
if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE || chunk_size > PAGE_SIZE) { @@ -336,19 +336,18 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) if ((addr + size) < addr) return -EINVAL;
- npgs = size >> PAGE_SHIFT; + npgs = div_u64_rem(size, PAGE_SIZE, &npgs_rem); + if (npgs_rem) + npgs++; if (npgs > U32_MAX) return -EINVAL;
- chunks = (unsigned int)div_u64(size, chunk_size); + chunks = (unsigned int)div_u64_rem(size, chunk_size, &chunks_rem); if (chunks == 0) return -EINVAL;
- if (!unaligned_chunks) { - chunks_per_page = PAGE_SIZE / chunk_size; - if (chunks < chunks_per_page || chunks % chunks_per_page) - return -EINVAL; - } + if (!unaligned_chunks && chunks_rem) + return -EINVAL;
if (headroom >= chunk_size - XDP_PACKET_HEADROOM) return -EINVAL;