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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/bpf.c
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@@ -112,7 +112,7 @@ int bpf_map_create(enum bpf_map_type map_type,
attr.map_type = map_type;
if (map_name)
strncat(attr.map_name, map_name, sizeof(attr.map_name) - 1);
libbpf_strlcpy(attr.map_name, map_name, sizeof(attr.map_name));
attr.key_size = key_size;
attr.value_size = value_size;
attr.max_entries = max_entries;
@@ -271,7 +271,7 @@ int bpf_prog_load_v0_6_0(enum bpf_prog_type prog_type,
attr.kern_version = OPTS_GET(opts, kern_version, 0);
if (prog_name)
strncat(attr.prog_name, prog_name, sizeof(attr.prog_name) - 1);
libbpf_strlcpy(attr.prog_name, prog_name, sizeof(attr.prog_name));
attr.license = ptr_to_u64(license);
if (insn_cnt > UINT_MAX)