linux-kernel - Re: [PATCH v2] x86/microcode: Silence a static checker warning

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Message-ID: <20170825090626.okc6reqltb5k4hip@pd.tnic>
Date:   Fri, 25 Aug 2017 11:06:26 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2] x86/microcode: Silence a static checker warning

Ok,

your initial patch was on the right track but let's simplify the whole
flow. That should not trigger your checker warning anymore:

---
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 59edbe9d4ccb..8f7a9bbad514 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -146,18 +146,18 @@ static bool microcode_matches(struct microcode_header_intel *mc_header,
 	return false;
 }
 
-static struct ucode_patch *__alloc_microcode_buf(void *data, unsigned int size)
+static struct ucode_patch *memdup_patch(void *data, unsigned int size)
 {
 	struct ucode_patch *p;
 
 	p = kzalloc(sizeof(struct ucode_patch), GFP_KERNEL);
 	if (!p)
-		return ERR_PTR(-ENOMEM);
+		return NULL;
 
 	p->data = kmemdup(data, size, GFP_KERNEL);
 	if (!p->data) {
 		kfree(p);
-		return ERR_PTR(-ENOMEM);
+		return NULL;
 	}
 
 	return p;
@@ -183,8 +183,8 @@ static void save_microcode_patch(void *data, unsigned int size)
 			if (mc_hdr->rev <= mc_saved_hdr->rev)
 				continue;
 
-			p = __alloc_microcode_buf(data, size);
-			if (IS_ERR(p))
+			p = memdup_patch(data, size);
+			if (!p)
 				pr_err("Error allocating buffer %p\n", data);
 			else
 				list_replace(&iter->plist, &p->plist);
@@ -196,24 +196,25 @@ static void save_microcode_patch(void *data, unsigned int size)
 	 * newly found.
 	 */
 	if (!prev_found) {
-		p = __alloc_microcode_buf(data, size);
-		if (IS_ERR(p))
+		p = memdup_patch(data, size);
+		if (!p)
 			pr_err("Error allocating buffer for %p\n", data);
 		else
 			list_add_tail(&p->plist, &microcode_cache);
 	}
 
+	if (!p)
+		return;
+
 	/*
 	 * Save for early loading. On 32-bit, that needs to be a physical
 	 * address as the APs are running from physical addresses, before
 	 * paging has been enabled.
 	 */
-	if (p) {
-		if (IS_ENABLED(CONFIG_X86_32))
-			intel_ucode_patch = (struct microcode_intel *)__pa_nodebug(p->data);
-		else
-			intel_ucode_patch = p->data;
-	}
+	if (IS_ENABLED(CONFIG_X86_32))
+		intel_ucode_patch = (struct microcode_intel *)__pa_nodebug(p->data);
+	else
+		intel_ucode_patch = p->data;
 }
 
 static int microcode_sanity_check(void *mc, int print_err)

-- 
Regards/Gruss,
    Boris.

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