linux-kernel - Re: [PATCH v2] vfs: constify arguments to utime family of system calls

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Message-ID: <20160401020524.GA17997@ZenIV.linux.org.uk>
Date:	Fri, 1 Apr 2016 03:05:24 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Eric Biggers <ebiggers3@...il.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vfs: constify arguments to utime family of system
 calls

On Thu, Mar 31, 2016 at 08:51:12PM -0500, Eric Biggers wrote:
> The system calls to set file times: utime(), utimes(), futimesat(), and
> utimensat(), all take in pointers to a filename and time information,
> neither of which is modified.  Mark the pointed-to data as 'const' to
> better reflect the semantics.

I'm not sure if there's any point, to be honest.  Anything doing direct
dereferencing of those pointers is completely broken and reads are no
better than writes in that respect.  OTOH... put_user() and friends will
produce an error when you give them const void __user * on most of the
architectures, so it's not entirely useles...

What's the situation with other syscalls?  It doesn't make much sense
to do it piece-by-piece...