linux-kernel - Re: [PATCH] ARM: mvebu: Prevent null pointer dereference caused by kzalloc failure

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Date: Sun, 25 Feb 2024 21:12:29 +0800 (GMT+08:00)
From: duoming@....edu.cn
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	andrew@...n.ch, gregory.clement@...tlin.com,
	sebastian.hesselbarth@...il.com
Subject: Re: [PATCH] ARM: mvebu: Prevent null pointer dereference caused by
 kzalloc failure

On Sun, 25 Feb 2024 11:29:53 +0000 Russell King (Oracle) wrote:
> > The kzalloc() in i2c_quirk() will return null if the physical
> > memory has run out. As a result, if we dereference the new_compat
> > pointer, the null pointer dereference bug will happen.
> > 
> > This patch adds a check to avoid null pointer dereference.
> 
> Yet again another janitorial patch that is Way too focused on a single
> issue, rather than analysing the code and proposing the best fix. :(
> 
> What if the two kstrdup() fail?

Thank you for your suggestions, I will also add a check to judge
whether two kstrdup() fail. The detail is shown below:

@@ -125,12 +125,20 @@ static void __init i2c_quirk(void)
                struct property *new_compat;

                new_compat = kzalloc(sizeof(*new_compat), GFP_KERNEL);
+               if(!new_compat)
+                       continue;

                new_compat->name = kstrdup("compatible", GFP_KERNEL);
                new_compat->length = sizeof("marvell,mv78230-a0-i2c");
                new_compat->value = kstrdup("marvell,mv78230-a0-i2c",
                                                GFP_KERNEL);

+               if (!new_compat->name || !new_compat->value) {
+                       kfree(new_compat->name);
+                       kfree(new_compat->value);
+                       kfree(new_compat);
+                       continue;
+               }
                of_update_property(np, new_compat);
        }
 }

Best regards,
Duoming Zhou