bpf, libbpf, smatch: Fix potential NULL pointer dereference

Based on the following report from Smatch, fix the potential NULL
pointer dereference check:

  tools/lib/bpf/libbpf.c:3493
  bpf_prog_load_xattr() warn: variable dereferenced before check 'attr'
  (see line 3483)

  3479 int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
  3480                         struct bpf_object **pobj, int *prog_fd)
  3481 {
  3482         struct bpf_object_open_attr open_attr = {
  3483                 .file           = attr->file,
  3484                 .prog_type      = attr->prog_type,
                                         ^^^^^^
  3485         };

At the head of function, it directly access 'attr' without checking
if it's NULL pointer. This patch moves the values assignment after
validating 'attr' and 'attr->file'.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
1 file changed
tree: 5d68119ecb6b6402500a1e7fbb10edbaa17d33ce
  1. include/
  2. scripts/
  3. src/
  4. travis-ci/
  5. .travis.yml
  6. CHECKPOINT-COMMIT
  7. meson.build
  8. README.md
README.md

This is a mirror of bpf-next linux tree's tools/lib/bpf directory plus its supporting header files.

The following files will by sync'ed with bpf-next repo:

  • src/ <-> bpf-next/tools/lib/bpf/
  • include/uapi/linux/bpf_common.h <-> bpf-next/tools/include/uapi/linux/bpf_common.h
  • include/uapi/linux/bpf.h <-> bpf-next/tools/include/uapi/linux/bpf.h
  • include/uapi/linux/btf.h <-> bpf-next/tools/include/uapi/linux/btf.h
  • include/uapi/linux/if_link.h <-> bpf-next/tools/include/uapi/linux/if_link.h
  • include/uapi/linux/if_xdp.h <-> bpf-next/tools/include/uapi/linux/if_xdp.h
  • include/uapi/linux/netlink.h <-> bpf-next/tools/include/uapi/linux/netlink.h
  • include/tools/libc_compat.h <-> bpf-next/tools/include/tools/libc_compat.h

Other header files at this repo (include/linux/*.h) are reduced versions of their counterpart files at bpf-next's tools/include/linux/*.h to make compilation successful.

Build Build Status

libelf is an internal dependency of libbpf and thus it is required to link against and must be installed on the system for applications to work. pkg-config is used by default to find libelf, and the program called can be overridden with PKG_CONFIG. If using pkg-config at build time is not desired, it can be disabled by setting NO_PKG_CONFIG=1 when calling make.

To build both static libbpf.a and shared libbpf.so:

$ cd src
$ make

To build only static libbpf.a library in directory build/ and install them together with libbpf headers in a staging directory root/:

$ cd src
$ mkdir build root
$ BUILD_STATIC_ONLY=y OBJDIR=build DESTDIR=root make install

To build both static libbpf.a and shared libbpf.so against a custom libelf dependency installed in /build/root/ and install them together with libbpf headers in a build directory /build/root/:

$ cd src
$ PKG_CONFIG_PATH=/build/root/lib64/pkgconfig DESTDIR=/build/root make install

To integrate libbpf into a project which uses Meson building system define [wrap-git] file in subprojects folder. To add libbpf dependency to the parent parent project, e.g. for libbpf_static_dep:

libbpf_obj = subproject('libbpf', required : true)
libbpf_static_dep = libbpf_proj.get_variable('libbpf_static_dep')

To validate changes to meson.build

$ python3 meson.py build
$ ninja -C build/

To install headers, libs and pkgconfig

$ cd build
$ ninja install