From: Magnus Karlsson <magnus.karlsson@intel.com> mainline inclusion from mainline-v5.7-rc2 commit 99e3a236dd43d06c65af0a2ef9cb44306aef6e02 category: bugfix bugzilla: 13690 CVE: CVE-2020-12659 ------------------------------------------------- Add a check that the headroom cannot be larger than the available space in the chunk. In the current code, a malicious user can set the headroom to a value larger than the chunk size minus the fixed XDP headroom. That way packets with a length larger than the supported size in the umem could get accepted and result in an out-of-bounds write. Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt") Reported-by: Bui Quang Minh <minhquangbui99@gmail.com> Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://bugzilla.kernel.org/show_bug.cgi?id=207225 Link: https://lore.kernel.org/bpf/1586849715-23490-1-git-send-email-magnus.karlsso... Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: net/xdp/xdp_umem.c [yyl: adjust context] Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> Reviewed-by: Wenan Mao <maowenan@huawei.com> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- net/xdp/xdp_umem.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c index b6d454c..bfd1b63 100644 --- a/net/xdp/xdp_umem.c +++ b/net/xdp/xdp_umem.c @@ -258,7 +258,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) u32 chunk_size = mr->chunk_size, headroom = mr->headroom; unsigned int chunks, chunks_per_page; u64 addr = mr->addr, size = mr->len; - int size_chk, err, i; + int err, i; if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE || chunk_size > PAGE_SIZE) { /* Strictly speaking we could support this, if: @@ -293,8 +293,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr) headroom = ALIGN(headroom, 64); - size_chk = chunk_size - headroom - XDP_PACKET_HEADROOM; - if (size_chk < 0) + if (headroom >= chunk_size - XDP_PACKET_HEADROOM) return -EINVAL; umem->address = (unsigned long)addr; -- 1.8.3