Commit 75ed82ea authored Sep 16, 2012 by Oleg Nesterov

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>

parent db023ea5

kernel/events/uprobes.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -221,7 +221,7 @@ static int write_opcode(struct arch_uprobe auprobe, struct mm_struct mm,

		retry:
		/* Read the page with vaddr into memory */
		ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma);
		ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &old_page, &vma);
		if (ret <= 0)
		return ret;

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