[PATCH] scsi: osst: Use struct_size() in kzalloc()

Gustavo A. R. Silva
2019-06-19T19:42:35Z

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 osst_buffer {
...
struct scatterlist sg[1]; /* MUST BE last item */
} ;

i = sizeof(struct osst_buffer) + (osst_max_sg_segs - 1) * sizeof(struct scatterlist);
instance = kzalloc(i, GFP_KERNEL);

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

instance = kzalloc(struct_size(instance, sg, count), GFP_KERNEL);

Notice that, in this case, variable i is not necessary, hence it
is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
drivers/scsi/osst.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/scsi/osst.c b/drivers/scsi/osst.c
index 815bb4097c1b..a11455a7e6bf 100644
--- a/drivers/scsi/osst.c
+++ b/drivers/scsi/osst.c
@@ -5307,7 +5307,6 @@ static long osst_compat_ioctl(struct file * file, unsigned int cmd_in, unsigned
/* Try to allocate a new tape buffer skeleton. Caller must not hold os_scsi_tapes_lock */
static struct osst_buffer * new_tape_buffer( int from_initialization, int need_dma, int max_sg )
{
- int i;
gfp_t priority;
struct osst_buffer *tb;

@@ -5316,8 +5315,7 @@ static struct osst_buffer * new_tape_buffer( int from_initialization, int need_d
else
priority = GFP_KERNEL;

- i = sizeof(struct osst_buffer) + (osst_max_sg_segs - 1) * sizeof(struct scatterlist);
- tb = kzalloc(i, priority);
+ tb = kzalloc(struct_size(tb, sg, osst_max_sg_segs - 1), priority);
if (!tb) {
printk(KERN_NOTICE "osst :I: Can't allocate new tape buffer.\n");
return NULL;
--
2.21.0