[PATCH v4 6/6] powerpc/eeh-powernv: fix potential OoB

[Markus Burri <markus.burri@mt.com>]

The buffer is set to 50 characters. If a caller write more characters,
count is truncated to the max available space in "simple_write_to_buffer".
To protect from OoB access, check that the input size fit into buffer and
add a zero terminator after copy to the end of the copied data.

Signed-off-by: Markus Burri <markus.burri@mt.com>
---
 arch/powerpc/platforms/powernv/eeh-powernv.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/eeh-powernv.c b/arch/powerpc/platforms/powernv/eeh-powernv.c
index db3370d1673c..3abee21fdd05 100644
--- a/arch/powerpc/platforms/powernv/eeh-powernv.c
+++ b/arch/powerpc/platforms/powernv/eeh-powernv.c
@@ -73,14 +73,19 @@ static ssize_t pnv_eeh_ei_write(struct file *filp,
 	char buf[50];
 	int ret;
 
+	if (count >= sizeof(buf))
+		return -EINVAL;
+
 	if (!eeh_ops || !eeh_ops->err_inject)
 		return -ENXIO;
 
 	/* Copy over argument buffer */
-	ret = simple_write_to_buffer(buf, sizeof(buf), ppos, user_buf, count);
+	ret = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, user_buf, count);
 	if (!ret)
 		return -EFAULT;
 
+	buf[ret] = '\0';
+
 	/* Retrieve parameters */
 	ret = sscanf(buf, "%x:%x:%x:%lx:%lx",
 		     &pe_no, &type, &func, &addr, &mask);
-- 
2.39.5