linux-kernel - [PATCH 2/2] compat_ioctl: do not hold BKL in handlers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <200910141800.36889.arnd@arndb.de>
Date:	Wed, 14 Oct 2009 18:00:36 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Vincent Sanders <vince@...tec.co.uk>,
	John Kacur <jkacur@...hat.com>,
	Jonathan Corbet <corbet@....net>,
	Christoph Hellwig <hch@...radead.org>, Greg KH <greg@...ah.com>
Subject: [PATCH 2/2] compat_ioctl: do not hold BKL in handlers

We have always called ioctl conversion handlers under the big
kernel lock, although that is generally not necessary. In particular
it is not needed for conversion of data structures and for calling
sys_ioctl or do_vfs_ioctl, which will get the BKL again if needed.

Handlers doing more than those two have been moved out, so we
can kill off the BKL from compat_sys_ioctl. This may significantly
improve latencies with 32 bit applications, and it avoids a common
scenario where a thread acquires the BKL twice.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 fs/compat_ioctl.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index 40904c6..320786e 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -2663,9 +2663,7 @@ asmlinkage long compat_sys_ioctl(unsigned int fd, unsigned int cmd,
 
  found_handler:
 	if (t->handler) {
-		lock_kernel();
 		error = t->handler(fd, cmd, arg, filp);
-		unlock_kernel();
 		goto out_fput;
 	}
 
-- 
1.6.3.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/