From: Oleg Nesterov <oleg@redhat.com>
Date: Sun, 16 Sep 2012 15:20:06 +0000 (+0200)
Subject: uprobes: Change write_opcode() to use FOLL_FORCE
X-Git-Tag: v3.7-rc3~40^2~1^2~13
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=75ed82ea53bd0d2d8083261123576250f7ba851e;p=pandora-kernel.git

uprobes: Change write_opcode() to use FOLL_FORCE

write_opcode()->get_user_pages() needs FOLL_FORCE to ensure we can
read the page even if the probed task did mprotect(PROT_NONE) after
uprobe_register(). Without FOLL_WRITE, FOLL_FORCE doesn't have any
side effect but allows to read the !VM_READ memory.

Otherwiese the subsequent uprobe_unregister()->set_orig_insn() fails
and we leak "int3". If that task does mprotect(PROT_READ | EXEC) and
execute the probed insn later it will be killed.

Note: in fact this is also needed for _register, see the next patch.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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