[PATCH 2/5] ipmi: ssif_bmc: fix missing check for copy_to_user() partial failure

[Jian Zhang]

copy_to_user() returns the number of bytes that could not be copied,
with a non-zero value indicating a partial or complete failure. The
current code only checks for negative return values and treats all
non-negative results as success.

Treating any positive return value from copy_to_user() as
an error and returning -EFAULT.

Fixes: dd2bc5cc9e25 ("ipmi: ssif_bmc: Add SSIF BMC driver")
Signed-off-by: Jian Zhang <zhangjian.3032@xxxxxxxxxxxxx>
---
 drivers/char/ipmi/ssif_bmc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
index 348e29490945..4037615ace12 100644
--- a/drivers/char/ipmi/ssif_bmc.c
+++ b/drivers/char/ipmi/ssif_bmc.c
@@ -163,6 +163,8 @@ static ssize_t ssif_bmc_read(struct file *file, char __user *buf, size_t count,
 		spin_unlock_irqrestore(&ssif_bmc->lock, flags);
 
 		ret = copy_to_user(buf, &msg, count);
+		if (ret > 0)
+			ret = -EFAULT;
 	}
 
 	return (ret < 0) ? ret : count;
-- 
2.20.1