linux-kernel - Re: [PATCH] stat: don't fail if the major number is >= 256

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Message-ID: <87tuayn284.fsf@igel.home>
Date:   Tue, 12 Apr 2022 10:19:07 +0200
From:   Andreas Schwab <schwab@...ux-m68k.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Mikulas Patocka <mpatocka@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH] stat: don't fail if the major number is >= 256

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@...ux-m68k.org
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