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bpf: Fix uninitialized values in BPF_{CORE,PROBE}_READ

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[ Upstream commit 41d4ce6df3f4945341ec509a840cc002a413b6cc ]

With the latest LLVM bpf selftests build will fail with
the following error message:

    progs/profiler.inc.h:710:31: error: default initialization of an object of type 'typeof ((parent_task)->real_cred->uid.val)' (aka 'const unsigned int') leaves the object uninitialized and is incompatible with C++ [-Werror,-Wdefault-const-init-unsafe]
      710 |         proc_exec_data->parent_uid = BPF_CORE_READ(parent_task, real_cred, uid.val);
          |                                      ^
    tools/testing/selftests/bpf/tools/include/bpf/bpf_core_read.h:520:35: note: expanded from macro 'BPF_CORE_READ'
      520 |         ___type((src), a, ##__VA_ARGS__) __r;                               \
          |                                          ^

This happens because BPF_CORE_READ (and other macro) declare the
variable __r using the ___type macro which can inherit const modifier
from intermediate types.

Fix this by using __typeof_unqual__, when supported. (And when it
is not supported, the problem shouldn't appear, as older compilers
haven't complained.)

Fixes: 792001f4f7 ("libbpf: Add user-space variants of BPF_CORE_READ() family of macros")
Fixes: a4b09a9ef9 ("libbpf: Add non-CO-RE variants of BPF_CORE_READ() macro family")
Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250502193031.3522715-1-a.s.protopopov@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Anton Protopopov
2025-05-02 19:30:31 +00:00
committed by Greg Kroah-Hartman
parent 7c4c84cdcc
commit c60f57a496
1 changed files with 6 additions and 0 deletions
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6
tools/lib/bpf/bpf_core_read.h
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@@ -312,7 +312,13 @@ enum bpf_enum_value_kind {
#define ___arrow10(a, b, c, d, e, f, g, h, i, j) a->b->c->d->e->f->g->h->i->j
#define ___arrow(...) ___apply(___arrow, ___narg(__VA_ARGS__))(__VA_ARGS__)
#if defined(__clang__) && (__clang_major__ >= 19)
#define ___type(...) __typeof_unqual__(___arrow(__VA_ARGS__))
#elif defined(__GNUC__) && (__GNUC__ >= 14)
#define ___type(...) __typeof_unqual__(___arrow(__VA_ARGS__))
#else
#define ___type(...) typeof(___arrow(__VA_ARGS__))
#endif
#define ___read(read_fn, dst, src_type, src, accessor) \
read_fn((void *)(dst), sizeof(*(dst)), &((src_type)(src))->accessor)