linux-kernel - [PATCH 2/3] Use _copy_from_user() to read SG iovec array.

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Message-ID: <04fbf8632f83496d819f27bb353dbf39@AcuMS.aculab.com>
Date:   Fri, 24 Jan 2020 15:46:00 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: [PATCH 2/3] Use _copy_from_user() to read SG iovec array.

The code has either just validated that the size fits in a caller supplied
fixed size buffer or has used kmalloc() to allocate a buffer.
So avoid the non-trivial cost of the HARDENED_USERCOPY checks by
calling _copy_from_user() instead of copy_from_user().

Signed-off-by: David Laight <david.laight@...lab.com>
---
 fs/read_write.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 441d9ca..0241d68 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -795,7 +795,7 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
 			goto out;
 		}
 	}
-	if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector))) {
+	if (_copy_from_user(iov, uvector, nr_segs*sizeof(*uvector))) {
 		ret = -EFAULT;
 		goto out;
 	}
-- 
1.8.1.2

-
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