linux-kernel - arch/x86/net/bpf_jit_comp.c:342:6: warning: Variable 'ret' is reassigned a value before the old one has been used.

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Date:   Fri, 7 Aug 2020 00:33:42 +0800
From:   kernel test robot <lkp@...el.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>
Subject: arch/x86/net/bpf_jit_comp.c:342:6: warning: Variable 'ret' is
 reassigned a value before the old one has been used.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   47ec5303d73ea344e84f46660fff693c57641386
commit: 428d5df1fa4f28daf622c48dd19da35585c9053c bpf, x86: Emit patchable direct jump as tail call
date:   9 months ago
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>


cppcheck warnings: (new ones prefixed by >>)

>> arch/x86/net/bpf_jit_comp.c:342:6: warning: Variable 'ret' is reassigned a value before the old one has been used. [redundantAssignment]
    ret = 0;
        ^
   arch/x86/net/bpf_jit_comp.c:334:6: note: Variable 'ret' is reassigned a value before the old one has been used.
    ret = -EBUSY;
        ^
   arch/x86/net/bpf_jit_comp.c:342:6: note: Variable 'ret' is reassigned a value before the old one has been used.
    ret = 0;
        ^
   arch/x86/net/bpf_jit_comp.c:409:2: warning: Signed integer overflow for expression '72+(139<<8)+(132<<16)+(214<<24)'. [integerOverflow]
    EMIT4_off32(0x48, 0x8B, 0x84, 0xD6,       /* mov rax, [rsi + rdx * 8 + offsetof(...)] */
    ^

vim +/ret +342 arch/x86/net/bpf_jit_comp.c

   267	
   268	static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
   269					void *old_addr, void *new_addr,
   270					const bool text_live)
   271	{
   272		int (*emit_patch_fn)(u8 **pprog, void *func, void *ip);
   273		const u8 *nop_insn = ideal_nops[NOP_ATOMIC5];
   274		u8 old_insn[X86_PATCH_SIZE] = {};
   275		u8 new_insn[X86_PATCH_SIZE] = {};
   276		u8 *prog;
   277		int ret;
   278	
   279		switch (t) {
   280		case BPF_MOD_NOP_TO_CALL ... BPF_MOD_CALL_TO_NOP:
   281			emit_patch_fn = emit_call;
   282			break;
   283		case BPF_MOD_NOP_TO_JUMP ... BPF_MOD_JUMP_TO_NOP:
   284			emit_patch_fn = emit_jump;
   285			break;
   286		default:
   287			return -ENOTSUPP;
   288		}
   289	
   290		switch (t) {
   291		case BPF_MOD_NOP_TO_CALL:
   292		case BPF_MOD_NOP_TO_JUMP:
   293			if (!old_addr && new_addr) {
   294				memcpy(old_insn, nop_insn, X86_PATCH_SIZE);
   295	
   296				prog = new_insn;
   297				ret = emit_patch_fn(&prog, new_addr, ip);
   298				if (ret)
   299					return ret;
   300				break;
   301			}
   302			return -ENXIO;
   303		case BPF_MOD_CALL_TO_CALL:
   304		case BPF_MOD_JUMP_TO_JUMP:
   305			if (old_addr && new_addr) {
   306				prog = old_insn;
   307				ret = emit_patch_fn(&prog, old_addr, ip);
   308				if (ret)
   309					return ret;
   310	
   311				prog = new_insn;
   312				ret = emit_patch_fn(&prog, new_addr, ip);
   313				if (ret)
   314					return ret;
   315				break;
   316			}
   317			return -ENXIO;
   318		case BPF_MOD_CALL_TO_NOP:
   319		case BPF_MOD_JUMP_TO_NOP:
   320			if (old_addr && !new_addr) {
   321				memcpy(new_insn, nop_insn, X86_PATCH_SIZE);
   322	
   323				prog = old_insn;
   324				ret = emit_patch_fn(&prog, old_addr, ip);
   325				if (ret)
   326					return ret;
   327				break;
   328			}
   329			return -ENXIO;
   330		default:
   331			return -ENOTSUPP;
   332		}
   333	
   334		ret = -EBUSY;
   335		mutex_lock(&text_mutex);
   336		if (memcmp(ip, old_insn, X86_PATCH_SIZE))
   337			goto out;
   338		if (text_live)
   339			text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
   340		else
   341			memcpy(ip, new_insn, X86_PATCH_SIZE);
 > 342		ret = 0;
   343	out:
   344		mutex_unlock(&text_mutex);
   345		return ret;
   346	}
   347	

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