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

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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: 3c0421c93ce4 ("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>
This commit is contained in:
Andrii Nakryiko
2025-06-06 13:21:34 -07:00
parent d3d933ac9b
commit 7356be641d
1 changed files with 3 additions and 3 deletions
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6
src/btf.c
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@@ -1384,12 +1384,12 @@ static struct btf *btf_parse_raw_mmap(const char *path, struct btf *base_btf)
fd = open(path, O_RDONLY); fd = open(path, O_RDONLY);
if (fd < 0) if (fd < 0)
return libbpf_err_ptr(-errno); return ERR_PTR(-errno);
if (fstat(fd, &st) < 0) { if (fstat(fd, &st) < 0) {
err = -errno; err = -errno;
close(fd); close(fd);
return libbpf_err_ptr(err); return ERR_PTR(err);
} }
data = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0); 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); close(fd);
if (data == MAP_FAILED) if (data == MAP_FAILED)
return libbpf_err_ptr(err); return ERR_PTR(err);
btf = btf_new(data, st.st_size, base_btf, true); btf = btf_new(data, st.st_size, base_btf, true);
if (IS_ERR(btf)) if (IS_ERR(btf))