[PATCH 4.14 43/66] md: avoid signed overflow in slot_store()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: NeilBrown <neilb@suse.de>

[ Upstream commit 3bc57292278a0b6ac4656cad94c14f2453344b57 ]

slot_store() uses kstrtouint() to get a slot number, but stores the
result in an "int" variable (by casting a pointer).
This can result in a negative slot number if the unsigned int value is
very large.

A negative number means that the slot is empty, but setting a negative
slot number this way will not remove the device from the array.  I don't
think this is a serious problem, but it could cause confusion and it is
best to fix it.

Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/md/md.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 880a0ebca8660..69d1501d9160e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2967,6 +2967,9 @@ slot_store(struct md_rdev *rdev, const char *buf, size_t len)
 		err = kstrtouint(buf, 10, (unsigned int *)&slot);
 		if (err < 0)
 			return err;
+		if (slot < 0)
+			/* overflow */
+			return -ENOSPC;
 	}
 	if (rdev->mddev->pers && slot == -1) {
 		/* Setting 'slot' on an active array requires also
-- 
2.39.2