linux-kernel - [57/74] random: drop weird m_time/a

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Date:	Thu, 04 Feb 2010 09:12:28 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [57/74] random: drop weird m_time/a_time manipulation

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Matt Mackall <mpm@...enic.com>

commit a996996dd75a9086b12d1cb4010f26e1748993f0 upstream.

No other driver does anything remotely like this that I know of except
for the tty drivers, and I can't see any reason for random/urandom to do
it. In fact, it's a (trivial, harmless) timing information leak. And
obviously, it generates power- and flash-cycle wasting I/O, especially
if combined with something like hwrngd. Also, it breaks ubifs's
expectations.

Signed-off-by: Matt Mackall <mpm@...enic.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/char/random.c |    8 --------
 1 file changed, 8 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1051,12 +1051,6 @@ random_read(struct file *file, char __us
 				/* like a named pipe */
 	}
 
-	/*
-	 * If we gave the user some bytes, update the access time.
-	 */
-	if (count)
-		file_accessed(file);
-
 	return (count ? count : retval);
 }
 
@@ -1116,8 +1110,6 @@ static ssize_t random_write(struct file
 	if (ret)
 		return ret;
 
-	inode->i_mtime = current_fs_time(inode->i_sb);
-	mark_inode_dirty(inode);
 	return (ssize_t)count;
 }
 


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