linux-kernel - [PATCH] compat_readv: Remove bogus area verify

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Message-Id: <1388193798-1966-1-git-send-email-cminyard@mvista.com>
Date:	Fri, 27 Dec 2013 19:23:18 -0600
From:	Corey Minyard <minyard@....org>
To:	Linux Kernel <linux-kernel@...r.kernel.org>
Cc:	Corey Minyard <cminyard@...sta.com>
Subject: [PATCH] compat_readv: Remove bogus area verify

The compat_do_readv_writev() function was doing a verify_area on the
incoming iov, but the nr_segs value is not checked.  If someone passes
in a -1 for nr_segs, for instance, the function should return an EINVAL.
However, it returns a EFAULT because the verify_area fails because it
is checking an array of size MAX_UINT.  The check is bogus, anyway,
because the next check, compat_rw_copy_check_uvector(), will do all
the necessary checking, anyway.  The non-compat do_readv_writev()
function doesn't do this check, so I think it's safe to just remove
the code.

Signed-off-by: Corey Minyard <cminyard@...sta.com>
---
 fs/read_write.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 58e440d..1193ffd 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -901,10 +901,6 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
 	io_fn_t fn;
 	iov_fn_t fnv;

-	ret = -EFAULT;
-	if (!access_ok(VERIFY_READ, uvector, nr_segs*sizeof(*uvector)))
-		goto out;
-
 	ret = compat_rw_copy_check_uvector(type, uvector, nr_segs,
 					       UIO_FASTIOV, iovstack, &iov);
 	if (ret <= 0)
-- 
1.8.3.1

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