Commit 5bd0190b authored Nov 29, 2005 by David Gibson Committed by Linus Torvalds Nov 29, 2005

[PATCH] Fix crash when ptrace poking hugepage areas



set_page_dirty() will not cope with being handed a page * which is part of
a compound page, but not the master page in that compound page.  This case
can occur via access_process_vm() if you attemp to write to another
process's hugepage memory area using ptrace() (causing an oops or hang).

This patch fixes the bug by only calling set_page_dirty() from
access_process_vm() if the page is not a compound page.  We already use a
similar fix in bio_set_pages_dirty() for the case of direct io to
hugepages.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: William Irwin <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent df69a60d

kernel/ptrace.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -241,6 +241,7 @@ int access_process_vm(struct task_struct tsk, unsigned long addr, void buf, in
		if (write) {
		copy_to_user_page(vma, page, addr,
		maddr + offset, buf, bytes);
		if (!PageCompound(page))
		set_page_dirty_lock(page);
		} else {
		copy_from_user_page(vma, page, addr,

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