From ba62d61128bda71fd02622f320ac59d861fc4baa Mon Sep 17 00:00:00 2001 From: Lorenz Bauer Date: Sat, 7 Oct 2023 00:06:51 +0200 Subject: [PATCH] bpf: Refuse unused attributes in bpf_prog_{attach,detach} The recently added tcx attachment extended the BPF UAPI for attaching and detaching by a couple of fields. Those fields are currently only supported for tcx, other types like cgroups and flow dissector silently ignore the new fields except for the new flags. This is problematic once we extend bpf_mprog to older attachment types, since it's hard to figure out whether the syscall really was successful if the kernel silently ignores non-zero values. Explicitly reject non-zero fields relevant to bpf_mprog for attachment types which don't use the latter yet. Fixes: e420bed02507 ("bpf: Add fd-based tcx multi-prog infra with link support") Signed-off-by: Lorenz Bauer Co-developed-by: Daniel Borkmann Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/r/20231006220655.1653-3-daniel@iogearbox.net Signed-off-by: Martin KaFai Lau --- kernel/bpf/syscall.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 453a43695a23ba..d77b2f8b93641b 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3796,7 +3796,6 @@ static int bpf_prog_attach(const union bpf_attr *attr) { enum bpf_prog_type ptype; struct bpf_prog *prog; - u32 mask; int ret; if (CHECK_ATTR(BPF_PROG_ATTACH)) @@ -3805,10 +3804,16 @@ static int bpf_prog_attach(const union bpf_attr *attr) ptype = attach_type_to_prog_type(attr->attach_type); if (ptype == BPF_PROG_TYPE_UNSPEC) return -EINVAL; - mask = bpf_mprog_supported(ptype) ? - BPF_F_ATTACH_MASK_MPROG : BPF_F_ATTACH_MASK_BASE; - if (attr->attach_flags & ~mask) - return -EINVAL; + if (bpf_mprog_supported(ptype)) { + if (attr->attach_flags & ~BPF_F_ATTACH_MASK_MPROG) + return -EINVAL; + } else { + if (attr->attach_flags & ~BPF_F_ATTACH_MASK_BASE) + return -EINVAL; + if (attr->relative_fd || + attr->expected_revision) + return -EINVAL; + } prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype); if (IS_ERR(prog)) @@ -3878,6 +3883,10 @@ static int bpf_prog_detach(const union bpf_attr *attr) if (IS_ERR(prog)) return PTR_ERR(prog); } + } else if (attr->attach_flags || + attr->relative_fd || + attr->expected_revision) { + return -EINVAL; } switch (ptype) {