md: avoid signed overflow in slot_store()

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>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index f548077..39e49e5 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3128,6 +3128,9 @@ 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