[PATCH 2/3] fsi: core: Use aligned_access_size() for cfam_read & cfam_write

[Jeremy Kerr]

The current offset/count calculations may result in an underflow, if the
resulting offset & 0x3 is larger than the count.

We have a function, aligned_access_size(), which does exactly this
calculation, so use that instead.

Signed-off-by: Jeremy Kerr <jk at codeconstruct.com.au>
Fixes: d1dcd6782576 ("fsi: Add cfam char devices")
Reported-by: Luo Likang <luolikang at nsfocus.com>
---
 drivers/fsi/fsi-core.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
index 92d6d9462e96..efd0d78ef234 100644
--- a/drivers/fsi/fsi-core.c
+++ b/drivers/fsi/fsi-core.c
@@ -708,8 +708,7 @@ static ssize_t cfam_read(struct file *filep, char __user *buf, size_t count,
 	for (total_len = 0; total_len < count; total_len += read_len) {
 		__be32 data;
 
-		read_len = min_t(size_t, count - total_len, 4);
-		read_len -= off & 0x3;
+		read_len = aligned_access_size(off, count - total_len);
 
 		rc = fsi_slave_read(slave, off, &data, read_len);
 		if (rc)
@@ -745,8 +744,7 @@ static ssize_t cfam_write(struct file *filep, const char __user *buf,
 	for (total_len = 0; total_len < count; total_len += write_len) {
 		__be32 data;
 
-		write_len = min_t(size_t, count - total_len, 4);
-		write_len -= off & 0x3;
+		write_len = aligned_access_size(off, count - total_len);
 
 		rc = copy_from_user(&data, buf + total_len, write_len);
 		if (rc) {
-- 
2.30.2