[char-misc-next 5/5] mei: revamp read and write length checks (no replies)

1. Return zero on zero length read and writes
2. For a too large write return -EFBIG as defined in man write(2)
EFBIG An attempt was made to write a file that
exceeds the implementation-defined maximum
file size or the process's file size limit,
or to write at a position past the maximum
allowed offset.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
---
drivers/misc/mei/main.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
index 5ff810b..7404584 100644
--- a/drivers/misc/mei/main.c
+++ b/drivers/misc/mei/main.c
@@ -203,12 +203,18 @@ static ssize_t mei_read(struct file *file, char __user *ubuf,

dev = cl->dev;

+
mutex_lock(&dev->device_lock);
if (dev->dev_state != MEI_DEV_ENABLED) {
rets = -ENODEV;
goto out;
}

+ if (length == 0) {
+ rets = 0;
+ goto out;
+ }
+
if (cl == &dev->iamthif_cl) {
rets = mei_amthif_read(dev, file, ubuf, length, offset);
goto out;
@@ -350,8 +356,14 @@ static ssize_t mei_write(struct file *file, const char __user *ubuf,
rets = -ENODEV;
goto out;
}
- if (length > dev->me_clients[id].props.max_msg_length || length <= 0) {
- rets = -EMSGSIZE;
+
+ if (length == 0) {
+ rets = 0;
+ goto out;
+ }
+
+ if (length > dev->me_clients[id].props.max_msg_length) {
+ rets = -EFBIG;
goto out;
}

--
1.8.3.1

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