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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Mark Rutland' <mark.rutland@arm.com>
CC:     'Szabolcs Nagy' <szabolcs.nagy@arm.com>,
        Theodore Ts'o <tytso@mit.edu>,
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        <linux-arm-kernel@lists.infradead.org>
Subject: RE: linux interprets an fcntl int arg as long
Thread-Topic: linux interprets an fcntl int arg as long
Thread-Index: AQHY7dH4b5GlkmHz9EyVI+/nub6Ts64p0qEQgAAgcACAAAds0IAAERqAgAADzNA=
Date:   Tue, 1 Nov 2022 13:29:41 +0000
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From: Mark Rutland
> Sent: 01 November 2022 13:13
> 
> On Tue, Nov 01, 2022 at 12:19:51PM +0000, David Laight wrote:
> > From: 'Szabolcs Nagy' <szabolcs.nagy@arm.com>
> > > Sent: 01 November 2022 11:45
> > >
> > > The 11/01/2022 10:02, David Laight wrote:
> > > > From: Szabolcs Nagy
> 
> > > kernel code:
> > > ------------
> > > SYSCALL_DEFINE3(fcntl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
> > > {
> >
> > That is just a wrapper and calls do_fcntl().
> > which needs changing to be add:
> > 	arg &= ~0U;
> > before the switch(cmd) {
> 
> Just to check, do you mean the switch in do_fcntl(), or the switch within memfd_fcntl() ?
> 
> The former handles other APIs which do expect arg to be a long (e.g.
> F_SET_RW_HINT and F_GET_RW_HINT expect it to hold a full 64-bit pointer), so
> that'd break things.

The assignment to argv is earlier.

	David

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