linux-kernel - [BUG] binfmt_elf: get_user() called in vma_dump_size() after set_fs(KERNEL

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Message-Id: <1233940235.22140.9.camel@localhost.localdomain>
Date:	Fri, 06 Feb 2009 18:10:35 +0100
From:	Gerald Schaefer <gerald.schaefer@...ibm.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [BUG] binfmt_elf: get_user() called in vma_dump_size() after
	set_fs(KERNEL_DS)

Hi,

elf_core_dump() does a set_fs(KERNEL_DS) and then calls vma_dump_size(),
which uses get_user() to check for an ELF header at vma->vm_start in the
user mapping. This is a bug because vm_start is a user virtual address and
get_user() will fail or even read from a kernel address (KERNEL_DS).

Maybe a get_user_pages() should be used to get the user data, or a temporary
set_fs(USER_DS)?

--
Gerald

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