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Subject[PATCH] md: dm-stripe: 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 stripe_c {
...
struct stripe stripe[0];
};

In this case alloc_context() and dm_array_too_big() are removed and
replaced by the direct use of the struct_size() helper in kmalloc().

Notice that open-coded form is prone to type mistakes.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
drivers/md/dm-stripe.c | 15 +--------------
include/linux/device-mapper.h | 3 ---
2 files changed, 1 insertion(+), 17 deletions(-)

diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 8547d7594338..63bbcc20f49a 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -55,19 +55,6 @@ static void trigger_event(struct work_struct *work)
dm_table_event(sc->ti->table);
}

-static inline struct stripe_c *alloc_context(unsigned int stripes)
-{
- size_t len;
-
- if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
- stripes))
- return NULL;
-
- len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
-
- return kmalloc(len, GFP_KERNEL);
-}
-
/*
* Parse a single <dev> <sector> pair
*/
@@ -142,7 +129,7 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
return -EINVAL;
}

- sc = alloc_context(stripes);
+ sc = kmalloc(struct_size(sc, stripe, stripes), GFP_KERNEL);
if (!sc) {
ti->error = "Memory allocation for striped context "
"failed";
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 399ad8632356..2e13826898b2 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -594,9 +594,6 @@ void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size);
*/
#define dm_round_up(n, sz) (dm_div_up((n), (sz)) * (sz))

-#define dm_array_too_big(fixed, obj, num) \
- ((num) > (UINT_MAX - (fixed)) / (obj))
-
/*
* Sector offset taken relative to the start of the target instead of
* relative to the start of the device.
--
2.23.0
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