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Jiayuan Chen says: ==================== bpf: Fix NULL-ptr-derefs when showing a void BTF type This series fixes three NULL-ptr-derefs in BTF handling. Patch 1 handles the syzbot report. A key-less BTF (btf_key_type_id == 0) used to be rejected for hash maps, until htab and rhtab gained a ->map_check_btf (to register a dtor) that does not look at the key, so a key-less hash map is now accepted. Dumping it through bpffs feeds the key type_id 0 into btf_type_seq_show() and NULL-derefs in btf_type_show(). Reject it again. Patches 2 and 3 fix two related, pre-existing crashes reachable via bpf_snprintf_btf(), which renders a type_id taken straight from the BPF program against the vmlinux BTF. A "const void" (a modifier resolving to void) NULL-derefs in btf_modifier_show() - void has no ->show op; a BTF_KIND_VAR NULL-derefs in btf_var_show() - the vmlinux base BTF has no resolved_ids. Patch 2 falls back to btf_df_show(), the "<unsupported kind:N>" placeholder already used for FWD/FUNC/FLOAT/DECL_TAG; patch 3 resolves the var's type directly, mirroring the existing guard in btf_modifier_show(). Patches 4 and 5 add selftests. Patch 4 checks a key-less hash and rhash map is rejected at creation. Patch 5 extends the snprintf_btf test to render a "const void" and a BTF_KIND_VAR from the vmlinux BTF and checks they resolve without crashing. v3 -> v4: Drop the pin-and-read reproducer from the key-less map test, fold the void/VAR test into the existing snprintf_btf test, and simplify patch 2's wording (review comments). v2 -> v3: Fold in a third fix for the same class of bug, btf_var_show(), reported while reviewing v2. Address review comments (Fixes attribution, verbatim syzbot trace, skip instead of fail). v1 -> v2: AI reported a pre-exist issue. Let's fold it in this series. v3: https://lore.kernel.org/bpf/20260831110314.150870-1-jiayuan.chen@linux.dev/ v2: https://lore.kernel.org/bpf/20260830073242.148092-1-jiayuan.chen@linux.dev/ v1: https://lore.kernel.org/bpf/20260828093142.179856-1-jiayuan.chen@linux.dev/ ==================== Link: https://patch.msgid.link/20260901104924.346187-1-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. 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