Commit 02670dee authored Jun 06, 2025 by Andrii Nakryiko Committed by Alexei Starovoitov Jun 06, 2025

libbpf: Handle unsupported mmap-based /sys/kernel/btf/vmlinux correctly



libbpf_err_ptr() helpers are meant to return NULL and set errno, if
there is an error. But btf_parse_raw_mmap() is meant to be used
internally and is expected to return ERR_PTR() values. Because of this
mismatch, when libbpf tries to mmap /sys/kernel/btf/vmlinux, we don't
detect the error correctly with IS_ERR() check, and never fallback to
old non-mmap-based way of loading vmlinux BTF.

Fix this by using proper ERR_PTR() returns internally.

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Fixes: 3c0421c9 ("libbpf: Use mmap to parse vmlinux BTF from sysfs")
Cc: Lorenz Bauer <lmb@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20250606202134.2738910-1-andrii@kernel.org


Signed-off-by: Alexei Starovoitov <ast@kernel.org>

parent 7a912d04

tools/lib/bpf/btf.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -1384,12 +1384,12 @@ static struct btf btf_parse_raw_mmap(const char path, struct btf *base_btf)

		fd = open(path, O_RDONLY);
		if (fd < 0)
		return libbpf_err_ptr(-errno);
		return ERR_PTR(-errno);

		if (fstat(fd, &st) < 0) {
		err = -errno;
		close(fd);
		return libbpf_err_ptr(err);
		return ERR_PTR(err);
		}

		data = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
		@@ -1397,7 +1397,7 @@ static struct btf btf_parse_raw_mmap(const char path, struct btf *base_btf)
		close(fd);

		if (data == MAP_FAILED)
		return libbpf_err_ptr(err);
		return ERR_PTR(err);

		btf = btf_new(data, st.st_size, base_btf, true);
		if (IS_ERR(btf))