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libbpf: Add sane strncpy alternative and use it internally

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strncpy() has a notoriously error-prone semantics which makes GCC
complain about it a lot (and quite often completely completely falsely
at that). Instead of pleasing GCC all the time (-Wno-stringop-truncation
is unfortunately only supported by GCC, so it's a bit too messy to just
enable it in Makefile), add libbpf-internal libbpf_strlcpy() helper
which follows what FreeBSD's strlcpy() does and what most people would
expect from strncpy(): copies up to N-1 first bytes from source string
into destination string and ensures zero-termination afterwards.

Replace all the relevant uses of strncpy/strncat/memcpy in libbpf with
libbpf_strlcpy().

This also fixes the issue reported by Emmanuel Deloget in xsk.c where
memcpy() could access source string beyond its end.

Fixes: 2f6324a3937f8 (libbpf: Support shared umems between queues and devices)
Reported-by: Emmanuel Deloget <emmanuel.deloget@eho.link>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211211004043.2374068-1-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko
2021-12-10 16:40:43 -08:00
committed by Andrii Nakryiko
parent df5689f1c8
commit a4e725f8f5
6 changed files with 31 additions and 19 deletions
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4
src/btf_dump.c
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@@ -2321,8 +2321,8 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
if (!opts->indent_str)
d->typed_dump->indent_str[0] = '\t';
else
strncat(d->typed_dump->indent_str, opts->indent_str,
sizeof(d->typed_dump->indent_str) - 1);
libbpf_strlcpy(d->typed_dump->indent_str, opts->indent_str,
sizeof(d->typed_dump->indent_str));
d->typed_dump->compact = OPTS_GET(opts, compact, false);
d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false);