linux-kernel - Re: [PATCH RESEND] coredump: Ensure proper size of sparse core files

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Message-Id: <20170116.224243.706466650029722351.davem@davemloft.net>
Date:   Mon, 16 Jan 2017 22:42:43 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     dave.kleikamp@...cle.com
Cc:     viro@...iv.linux.org.uk, sparclinux@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] coredump: Ensure proper size of sparse core
 files

From: Dave Kleikamp <dave.kleikamp@...cle.com>
Date: Wed, 11 Jan 2017 13:25:00 -0600

> If the last section of a core file ends with an unmapped or zero page,
> the size of the file does not correspond with the last dump_skip() call.
> gdb complains that the file is truncated and can be confusing to users.
> 
> After all of the vma sections are written, make sure that the file size
> is no smaller than the current file position.
> 
> This problem can be demonstrated with gdb's bigcore testcase on the
> sparc architecture.
> 
> Signed-off-by: Dave Kleikamp <dave.kleikamp@...cle.com>

The lseek() done by dump_skip() should extend the file properly.

Otherwise, everyone would be seeing this problem.

That test case passed all the time when I was last running the GDB
testsuite all the time on sparc64, say 5 years ago.