libbpf: Fix realloc API handling in zero-sized edge cases
realloc() and reallocarray() can either return NULL or a special non-NULL pointer, if their size argument is zero. This requires a bit more care to handle NULL-as-valid-result situation differently from NULL-as-error case. This has caused real issues before ([0]), and just recently bit again in production when performing bpf_program__attach_usdt(). This patch fixes 4 places that do or potentially could suffer from this mishandling of NULL, including the reported USDT-related one. There are many other places where realloc()/reallocarray() is used and NULL is always treated as an error value, but all those have guarantees that their size is always non-zero, so those spot don't need any extra handling. [0] d08ab82f ("libbpf: Fix double-free when linker processes empty sections") Fixes: 999783c8 ("libbpf: Wire up spec management and other arch-independent USDT logic") Fixes: b63b3c49 ("libbpf: Add bpf_program__set_insns function") Fixes: 697f104d ("libbpf: Support custom SEC() handlers") Fixes: b1268826 ("libbpf: Change the order of data and text relocations.") Signed-off-by:Andrii Nakryiko <andrii@kernel.org> Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20230711024150.1566433-1-andrii@kernel.org
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