linux.git/tools/lib/bpf/linker.c, branch v6.7

libbpf: Fix double-free when linker processes empty sections

2023-03-28T03:02:15+00:00

Double-free error in bpf_linker__free() was reported by James Hilliard.
The error is caused by miss-use of realloc() in extend_sec().
The error occurs when two files with empty sections of the same name
are linked:
- when first file is processed:
  - extend_sec() calls realloc(dst->raw_data, dst_align_sz)
    with dst->raw_data == NULL and dst_align_sz == 0;
  - dst->raw_data is set to a special pointer to a memory block of
    size zero;
- when second file is processed:
  - extend_sec() calls realloc(dst->raw_data, dst_align_sz)
    with dst->raw_data ==  and dst_align_sz == 0;
  - realloc() "frees" dst->raw_data special pointer and returns NULL;
  - extend_sec() exits with -ENOMEM, and the old dst->raw_data value
    is preserved (it is now invalid);
  - eventually, bpf_linker__free() attempts to free dst->raw_data again.

This patch fixes the bug by avoiding -ENOMEM exit for dst_align_sz == 0.
The fix was suggested by Andrii Nakryiko .

Reported-by: James Hilliard 
Signed-off-by: Eduard Zingerman 
Signed-off-by: Andrii Nakryiko 
Tested-by: James Hilliard 
Link: https://lore.kernel.org/bpf/CADvTj4o7ZWUikKwNTwFq0O_AaX+46t_+Ca9gvWMYdWdRtTGeHQ@mail.gmail.com/
Link: https://lore.kernel.org/bpf/20230328004738.381898-3-eddyz87@gmail.com

libbpf: Cleanup linker_append_elf_relos

2023-03-01T19:13:11+00:00

Clang Static Analyser (scan-build) reports some unused symbols and dead
assignments in the linker_append_elf_relos function. Clean these up.

Signed-off-by: Viktor Malik 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/c5c8fe9f411b69afada8399d23bb048ef2a70535.1677658777.git.vmalik@redhat.com

libbpf: Add enum64 support for bpf linking

2022-06-07T17:20:43+00:00

Add BTF_KIND_ENUM64 support for bpf linking, which is
very similar to BTF_KIND_ENUM.

Acked-by: Andrii Nakryiko 
Signed-off-by: Yonghong Song 
Link: https://lore.kernel.org/r/20220607062642.3721494-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov

libbpf: Fix is_pow_of_2

2022-06-03T21:53:33+00:00

Move the correct definition from linker.c into libbpf_internal.h.

Fixes: 0087a681fa8c ("libbpf: Automatically fix up BPF_MAP_TYPE_RINGBUF size, if necessary")
Reported-by: Yuze Chi 
Signed-off-by: Yuze Chi 
Signed-off-by: Ian Rogers 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20220603055156.2830463-1-irogers@google.com

libbpf: Fix using invalidated memory in bpf_linker

2021-11-25T23:15:03+00:00

add_dst_sec() can invalidate bpf_linker's section index making
dst_symtab pointer pointing into unallocated memory. Reinitialize
dst_symtab pointer on each iteration to make sure it's always valid.

Fixes: faf6ed321cf6 ("libbpf: Add BPF static linker APIs")
Signed-off-by: Andrii Nakryiko 
Signed-off-by: Daniel Borkmann 
Link: https://lore.kernel.org/bpf/20211124002325.1737739-7-andrii@kernel.org

libbpf: Fix glob_syms memory leak in bpf_linker

2021-11-25T23:15:02+00:00

glob_syms array wasn't freed on bpf_link__free(). Fix that.

Fixes: a46349227cd8 ("libbpf: Add linker extern resolution support for functions and global variables")
Signed-off-by: Andrii Nakryiko 
Signed-off-by: Daniel Borkmann 
Link: https://lore.kernel.org/bpf/20211124002325.1737739-6-andrii@kernel.org

libbpf: Turn btf_dedup_opts into OPTS-based struct

2021-11-12T00:54:05+00:00

btf__dedup() and struct btf_dedup_opts were added before we figured out
OPTS mechanism. As such, btf_dedup_opts is non-extensible without
breaking an ABI and potentially crashing user application.

Unfortunately, btf__dedup() and btf_dedup_opts are short and succinct
names that would be great to preserve and use going forward. So we use
___libbpf_override() macro approach, used previously for bpf_prog_load()
API, to define a new btf__dedup() variant that accepts only struct btf *
and struct btf_dedup_opts * arguments, and rename the old btf__dedup()
implementation into btf__dedup_deprecated(). This keeps both source and
binary compatibility with old and new applications.

The biggest problem was struct btf_dedup_opts, which wasn't OPTS-based,
and as such doesn't have `size_t sz;` as a first field. But btf__dedup()
is a pretty rarely used API and I believe that the only currently known
users (besides selftests) are libbpf's own bpf_linker and pahole.
Neither use case actually uses options and just passes NULL. So instead
of doing extra hacks, just rewrite struct btf_dedup_opts into OPTS-based
one, move btf_ext argument into those opts (only bpf_linker needs to
dedup btf_ext, so it's not a typical thing to specify), and drop never
used `dont_resolve_fwds` option (it was never used anywhere, AFAIK, it
makes BTF dedup much less useful and efficient).

Just in case, for old implementation, btf__dedup_deprecated(), detect
non-NULL options and error out with helpful message, to help users
migrate, if there are any user playing with btf__dedup().

The last remaining piece is dedup_table_size, which is another
anachronism from very early days of BTF dedup. Since then it has been
reduced to the only valid value, 1, to request forced hash collisions.
This is only used during testing. So instead introduce a bool flag to
force collisions explicitly.

This patch also adapts selftests to new btf__dedup() and btf_dedup_opts
use to avoid selftests breakage.

  [0] Closes: https://github.com/libbpf/libbpf/issues/281

Signed-off-by: Andrii Nakryiko 
Signed-off-by: Alexei Starovoitov 
Link: https://lore.kernel.org/bpf/20211111053624.190580-4-andrii@kernel.org

libbpf: Use O_CLOEXEC uniformly when opening fds

2021-10-28T23:30:07+00:00

There are some instances where we don't use O_CLOEXEC when opening an
fd, fix these up. Otherwise, it is possible that a parallel fork causes
these fds to leak into a child process on execve.

Signed-off-by: Kumar Kartikeya Dwivedi 
Signed-off-by: Alexei Starovoitov 
Acked-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20211028063501.2239335-6-memxor@gmail.com

libbpf: Use __BYTE_ORDER__

2021-10-26T03:39:41+00:00

Use the compiler-defined __BYTE_ORDER__ instead of the libc-defined
__BYTE_ORDER for consistency.

Signed-off-by: Ilya Leoshkevich 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20211026010831.748682-3-iii@linux.ibm.com

libbpf: Add btf__type_cnt() and btf__raw_data() APIs

2021-10-22T23:09:14+00:00

Add btf__type_cnt() and btf__raw_data() APIs and deprecate
btf__get_nr_type() and btf__get_raw_data() since the old APIs
don't follow the libbpf naming convention for getters which
omit 'get' in the name (see [0]). btf__raw_data() is just an
alias to the existing btf__get_raw_data(). btf__type_cnt()
now returns the number of all types of the BTF object
including 'void'.

  [0] Closes: https://github.com/libbpf/libbpf/issues/279

Signed-off-by: Hengqi Chen 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20211022130623.1548429-2-hengqi.chen@gmail.com