treewide: Use struct_size() for kmalloc()-family

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 foo {
    int stuff;
    void *entry[];
};

instance = kmalloc(sizeof(struct foo) + sizeof(void *) * 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, entry, count), GFP_KERNEL);

This patch makes the changes for kmalloc()-family (and kvmalloc()-family)
uses. It was done via automatic conversion with manual review for the
"CHECKME" non-standard cases noted below, using the following Coccinelle
script:

// pkey_cache = kmalloc(sizeof *pkey_cache + tprops->pkey_tbl_len *
//                      sizeof *pkey_cache->table, GFP_KERNEL);
@@
identifier alloc =~ "kmalloc|kzalloc|kvmalloc|kvzalloc";
expression GFP;
identifier VAR, ELEMENT;
expression COUNT;
@@

- alloc(sizeof(*VAR) + COUNT * sizeof(*VAR->ELEMENT), GFP)
+ alloc(struct_size(VAR, ELEMENT, COUNT), GFP)

// mr = kzalloc(sizeof(*mr) + m * sizeof(mr->map[0]), GFP_KERNEL);
@@
identifier alloc =~ "kmalloc|kzalloc|kvmalloc|kvzalloc";
expression GFP;
identifier VAR, ELEMENT;
expression COUNT;
@@

- alloc(sizeof(*VAR) + COUNT * sizeof(VAR->ELEMENT[0]), GFP)
+ alloc(struct_size(VAR, ELEMENT, COUNT), GFP)

// Same pattern, but can't trivially locate the trailing element name,
// or variable name.
@@
identifier alloc =~ "kmalloc|kzalloc|kvmalloc|kvzalloc";
expression GFP;
expression SOMETHING, COUNT, ELEMENT;
@@

- alloc(sizeof(SOMETHING) + COUNT * sizeof(ELEMENT), GFP)
+ alloc(CHECKME_struct_size(&SOMETHING, ELEMENT, COUNT), GFP)

Signed-off-by: Kees Cook <keescook@chromium.org>

2 files changed, 2 insertions, 4 deletions

diff --git a/drivers/clk/berlin/bg2.c b/drivers/clk/berlin/bg2.c
index e7331ace0337..45fb888bf0a0 100644
--- a/drivers/clk/berlin/bg2.c
+++ b/drivers/clk/berlin/bg2.c
@@ -509,8 +509,7 @@ static void __init berlin2_clock_setup(struct device_node *np)
 	u8 avpll_flags = 0;
 	int n, ret;
 
-	clk_data = kzalloc(sizeof(*clk_data) +
-			   sizeof(*clk_data->hws) * MAX_CLKS, GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, MAX_CLKS), GFP_KERNEL);
 	if (!clk_data)
 		return;
 	clk_data->num = MAX_CLKS;
diff --git a/drivers/clk/berlin/bg2q.c b/drivers/clk/berlin/bg2q.c
index 67c270b143f7..db7364e15c8b 100644
--- a/drivers/clk/berlin/bg2q.c
+++ b/drivers/clk/berlin/bg2q.c
@@ -295,8 +295,7 @@ static void __init berlin2q_clock_setup(struct device_node *np)
 	struct clk_hw **hws;
 	int n, ret;
 
-	clk_data = kzalloc(sizeof(*clk_data) +
-			   sizeof(*clk_data->hws) * MAX_CLKS, GFP_KERNEL);
+	clk_data = kzalloc(struct_size(clk_data, hws, MAX_CLKS), GFP_KERNEL);
 	if (!clk_data)
 		return;
 	clk_data->num = MAX_CLKS;