bpf: Fix re-attachment branch in bpf_tracing_prog_attach

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix re-attachment branch in bpf_tracing_prog_attach The following case can cause a crash due to missing attach_btf: 1) load rawtp program 2) load fentry program with rawtp as target_fd 3) create tracing link for fentry program with target_fd = 0 4) repeat 3 In the end we have: - prog->aux->dst_trampoline == NULL - tgt_prog == NULL (because we did not provide target_fd to link_create) - prog->aux->attach_btf == NULL (the program was loaded with attach_prog_fd=X) - the program was loaded for tgt_prog but we have no way to find out which one BUG: kernel NULL pointer dereference, address: 0000000000000058 Call Trace: <TASK> ? __die+0x20/0x70 ? page_fault_oops+0x15b/0x430 ? fixup_exception+0x22/0x330 ? exc_page_fault+0x6f/0x170 ? asm_exc_page_fault+0x22/0x30 ? bpf_tracing_prog_attach+0x279/0x560 ? btf_obj_id+0x5/0x10 bpf_tracing_prog_attach+0x439/0x560 __sys_bpf+0x1cf4/0x2de0 __x64_sys_bpf+0x1c/0x30 do_syscall_64+0x41/0xf0 entry_SYSCALL_64_after_hwframe+0x6e/0x76 Return -EINVAL in this situation.

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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，该漏洞源于缺少attach_btf而导致崩溃。

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