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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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6
src/gen_loader.c
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@@ -463,8 +463,7 @@ void bpf_gen__map_create(struct bpf_gen *gen,
attr.map_flags = map_attr->map_flags;
attr.map_extra = map_attr->map_extra;
if (map_name)
memcpy(attr.map_name, map_name,
min((unsigned)strlen(map_name), BPF_OBJ_NAME_LEN - 1));
libbpf_strlcpy(attr.map_name, map_name, sizeof(attr.map_name));
attr.numa_node = map_attr->numa_node;
attr.map_ifindex = map_attr->map_ifindex;
attr.max_entries = max_entries;
@@ -970,8 +969,7 @@ void bpf_gen__prog_load(struct bpf_gen *gen,
core_relos = add_data(gen, gen->core_relos,
attr.core_relo_cnt * attr.core_relo_rec_size);
memcpy(attr.prog_name, prog_name,
min((unsigned)strlen(prog_name), BPF_OBJ_NAME_LEN - 1));
libbpf_strlcpy(attr.prog_name, prog_name, sizeof(attr.prog_name));
prog_load_attr = add_data(gen, &attr, attr_size);
/* populate union bpf_attr with a pointer to license */