CVE-2026-43333— bpf: reject direct access to nullable PTR_TO_BUF pointers

bpf: reject direct access to nullable PTR_TO_BUF pointers

In the Linux kernel, the following vulnerability has been resolved: bpf: reject direct access to nullable PTR_TO_BUF pointers check_mem_access() matches PTR_TO_BUF via base_type() which strips PTR_MAYBE_NULL, allowing direct dereference without a null check. Map iterator ctx->key and ctx->value are PTR_TO_BUF | PTR_MAYBE_NULL. On stop callbacks these are NULL, causing a kernel NULL dereference. Add a type_may_be_null() guard to the PTR_TO_BUF branch, matching the existing PTR_TO_BTF_ID pattern.

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Linux kernel 安全漏洞

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于BPF中check_mem_access函数通过base_type匹配PTR_TO_BUF指针时未检查PTR_MAYBE_NULL标志，允许直接解引用空指针，导致内核空指针解引用。

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