linux-kernel - Re: [RFC][PATCH 0/4] Check O_* flags set with fcntl() on anon

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Date:	Sun, 14 Feb 2010 03:52:05 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Matt Helsley <matthltc@...ibm.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 0/4] Check O_* flags set with fcntl() on anon_inode
 files.

On Sat, Feb 13, 2010 at 04:27:43PM -0800, Matt Helsley wrote:
> anon_inode interfaces often do not support flags that can be set
> by fcntl(). Right now using fcntl() to set these flags falsely
> reports success for things like O_ASYNC yet SIGIO is not delivered.
> 
> I relied on the flags allowed by the syscalls that create
> these files to determine the flags that are allowed to be set by
> fcntl().
> 
> Each patch checks flags for one anonymous inode interface:
> 
> [PATCH 1/4] signalfd
> [PATCH 2/4] timerfd
> [PATCH 3/4] epoll
> [PATCH 4/4] eventfd
> 
> I did not check the perf, kvm-vm, or kvm-vcpu uses of anon_inodes.

Er...  O_ASYNC is silently ignored for regular files as well, so any
userland code that tries to rely on fcntl() rejecting it is and always
had been badly b0rken.
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