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From:   Andreas Schwab <schwab@linux-m68k.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Mikulas Patocka <mpatocka@redhat.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH] stat: don't fail if the major number is >= 256
References: <alpine.LRH.2.02.2204111023230.6206@file01.intranet.prod.int.rdu2.redhat.com>
        <CAHk-=wijDnLH2K3Rh2JJo-SmWL_ntgzQCDxPeXbJ9A-vTF3ZvA@mail.gmail.com>
        <alpine.LRH.2.02.2204111236390.31647@file01.intranet.prod.int.rdu2.redhat.com>
        <CAHk-=wgsHK4pDDoEgCyKgGyo-AMGpy1jg2QbstaCR0G-v568yg@mail.gmail.com>
Date:   Tue, 12 Apr 2022 10:19:07 +0200
In-Reply-To: <CAHk-=wgsHK4pDDoEgCyKgGyo-AMGpy1jg2QbstaCR0G-v568yg@mail.gmail.com>
        (Linus Torvalds's message of "Mon, 11 Apr 2022 19:37:44 -1000")
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On Apr 11 2022, Linus Torvalds wrote:

>> For me, the failure happens in cp_compat_stat (I have a 64-bit kernel). In
>> struct compat_stat in arch/x86/include/asm/compat.h, st_dev and st_rdev
>> are compat_dev_t which is 16-bit. But they are followed by 16-bit
>> paddings, so they could be extended.
>
> Ok, that actually looks like a bug.
>
> The compat structure should match the native structure.  Those "u16
> __padX" fields seem to be just a symptom of the bug.

Looks like the move to 32-bit st_[r]dev was never applied to struct
compat_stat, see commit e95b206567 ("[PATCH] struct stat - support
larger dev_t") from tglx/history.git.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."