linux-kernel - [PATCH 2/2 V2] livepatch: handle kzalloc failure properly

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Message-Id: <1544709956-16701-2-git-send-email-hofrat@osadl.org>
Date:   Thu, 13 Dec 2018 15:05:56 +0100
From:   Nicholas Mc Guire <hofrat@...dl.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Jessica Yu <jeyu@...nel.org>, Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org, Nicholas Mc Guire <hofrat@...dl.org>
Subject: [PATCH 2/2 V2] livepatch: handle kzalloc failure properly

kzalloc() return should be checked. On dummy_alloc() failing
in kzalloc() NULL should be returned.

Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
---

Problem was located with an experimental coccinelle script

V2: returning NULL is ok but not without cleanup - thanks to
    Petr Mladek <pmladek@...e.com> for catching this.

Patch was compile tested with: x86_64_defconfig + FTRACE=y
FUNCTION_TRACER=y, EXPERT=y, LATENCYTOP=y, SAMPLES=y, SAMPLE_LIVEPATCH=y
(with a number of unrelated sparse warnings on symbols not being static)

Patch is against 4.20-rc6 (localversion-next is next-20181213)

 samples/livepatch/livepatch-shadow-mod.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/samples/livepatch/livepatch-shadow-mod.c b/samples/livepatch/livepatch-shadow-mod.c
index 4c54b25..4aa8a88 100644
--- a/samples/livepatch/livepatch-shadow-mod.c
+++ b/samples/livepatch/livepatch-shadow-mod.c
@@ -118,6 +118,10 @@ noinline struct dummy *dummy_alloc(void)
 
 	/* Oops, forgot to save leak! */
 	leak = kzalloc(sizeof(int), GFP_KERNEL);
+	if (!leak) {
+		kfree(d);
+		return NULL;
+	}
 
 	pr_info("%s: dummy @ %p, expires @ %lx\n",
 		__func__, d, d->jiffies_expire);
-- 
2.1.4