linux-kernel - [PATCH] tracepoint: Use struct

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Message-ID: <20190610212219.GA27692@embeddedor>
Date:   Mon, 10 Jun 2019 16:22:19 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] tracepoint: Use struct_size() in kmalloc()

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct tp_probes {
	...
        struct tracepoint_func probes[0];
};

instance = kmalloc(sizeof(sizeof(struct tp_probes) +
			sizeof(struct tracepoint_func) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kmalloc(struct_size(instance, probes, count) GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 kernel/tracepoint.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index df3ade14ccbd..73956eaff8a9 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -55,8 +55,8 @@ struct tp_probes {
 
 static inline void *allocate_probes(int count)
 {
-	struct tp_probes *p  = kmalloc(count * sizeof(struct tracepoint_func)
-			+ sizeof(struct tp_probes), GFP_KERNEL);
+	struct tp_probes *p  = kmalloc(struct_size(p, probes, count),
+				       GFP_KERNEL);
 	return p == NULL ? NULL : p->probes;
 }
 
-- 
2.21.0