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[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>
This commit is contained in:
David Gibson 2005-11-29 19:34:32 -08:00 committed by Linus Torvalds
parent df69a60dc6
commit 5bd0190bf3
1 changed files with 2 additions and 1 deletions
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3
kernel/ptrace.c
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@ -241,7 +241,8 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in
if (write) { if (write) {
copy_to_user_page(vma, page, addr, copy_to_user_page(vma, page, addr,
maddr + offset, buf, bytes); maddr + offset, buf, bytes);
set_page_dirty_lock(page); if (!PageCompound(page))
set_page_dirty_lock(page);
} else { } else {
copy_from_user_page(vma, page, addr, copy_from_user_page(vma, page, addr,
buf, maddr + offset, bytes); buf, maddr + offset, bytes);