linux-kernel - [PATCH 1/2 V2] livepatch: handle kzalloc failure properly

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Date:   Thu, 13 Dec 2018 15:05:55 +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 1/2 V2] livepatch: handle kzalloc failure properly

kzalloc() return should always be checked - notably in example code
where this may be seen as reference. On failure of allocation
livepatch_fix1_dummy_alloc() should return NULL.

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

Problem was located with an experimental coccinelle script

V2: ...and since it is reference code the fix should be correct as well...
    thanks to Petr Mladek <pmladek@...e.com> for catching the missing
    kfree().

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

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

 samples/livepatch/livepatch-shadow-fix1.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/samples/livepatch/livepatch-shadow-fix1.c b/samples/livepatch/livepatch-shadow-fix1.c
index 49b1355..e8f1bd6 100644
--- a/samples/livepatch/livepatch-shadow-fix1.c
+++ b/samples/livepatch/livepatch-shadow-fix1.c
@@ -89,6 +89,11 @@ struct dummy *livepatch_fix1_dummy_alloc(void)
 	 * pointer to handle resource release.
 	 */
 	leak = kzalloc(sizeof(int), GFP_KERNEL);
+	if (!leak) {
+		kfree(d);
+		return NULL;
+	}
+
 	klp_shadow_alloc(d, SV_LEAK, sizeof(leak), GFP_KERNEL,
 			 shadow_leak_ctor, leak);
 
-- 
2.1.4