linux-kernel - [PATCH] mm: Return -EFAULT if copy_to

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Date:   Mon,  1 Mar 2021 20:32:43 +0800
From:   Wang Qing <wangqing@...o.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Wang Qing <wangqing@...o.com>
Subject: [PATCH] mm: Return -EFAULT if copy_to_user() fails

The copy_to_user() function returns the number of bytes remaining to be
copied, but we want to return -EFAULT if the copy doesn't complete.

Signed-off-by: Wang Qing <wangqing@...o.com>
---
 mm/mempolicy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index ab51132..a116e56
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1667,7 +1667,7 @@ COMPAT_SYSCALL_DEFINE5(get_mempolicy, int __user *, policy,
 	if (!err && nmask) {
 		unsigned long copy_size;
 		copy_size = min_t(unsigned long, sizeof(bm), alloc_size);
-		err = copy_from_user(bm, nm, copy_size);
+		err = copy_from_user(bm, nm, copy_size) ? -EFAULT : 0;
 		/* ensure entire bitmap is zeroed */
 		err |= clear_user(nmask, ALIGN(maxnode-1, 8) / 8);
 		err |= compat_put_bitmap(nmask, bm, nr_bits);
-- 
2.7.4