There are currently two ways to modify a kernel memory in bpf programs: 1. declare a ksym of scalar type and directly modify its memory. 2. Pass a RDONLY_BUF into a helper function which will override its arguments. For example, bpf_d_path, bpf_snprintf. This patchset fixes these two problem. For the first, we introduce a new reg type PTR_TO_RDONLY_MEM for the scalar typed ksym, which forbids writing. For the second, we introduce a new arg type ARG_CONST_PTR_TO_MEM to differentiate the arg types that only read the memory from those that may write the memory. The previous ARG_PTR_TO_MEM is now only compatible with writable memories. If a helper doesn't write into its argument, it can use ARG_CONST_PTR_TO_MEM, which is also compatible with read-only memories. In v2, Andrii suggested using the name "ARG_PTR_TO_RDONLY_MEM", but I find it is sort of misleading. Because the new arg_type is compatible with both write and read-only memory. So I chose ARG_CONST_PTR_TO_MEM instead. Hao Luo (3): bpf: Prevent write to ksym memory bpf: Introduce ARG_CONST_PTR_TO_MEM bpf/selftests: Test PTR_TO_RDONLY_MEM include/linux/bpf.h | 20 +++++- include/uapi/linux/bpf.h | 4 +- kernel/bpf/btf.c | 2 +- kernel/bpf/cgroup.c | 2 +- kernel/bpf/helpers.c | 12 ++-- kernel/bpf/ringbuf.c | 2 +- kernel/bpf/syscall.c | 2 +- kernel/bpf/verifier.c | 60 +++++++++++++---- kernel/trace/bpf_trace.c | 26 ++++---- net/core/filter.c | 64 +++++++++---------- tools/include/uapi/linux/bpf.h | 4 +- .../selftests/bpf/prog_tests/ksyms_btf.c | 14 ++++ .../bpf/progs/test_ksyms_btf_write_check.c | 29 +++++++++ 13 files changed, 168 insertions(+), 73 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf_write_check.c -- 2.34.0.rc0.344.g81b53c2807-goog
