Commit 5bd0190b authored by David Gibson's avatar David Gibson Committed by Linus Torvalds
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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

Signed-off-by: default avatarDavid Gibson <>
Acked-by: default avatarWilliam Irwin <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent df69a60d
......@@ -241,7 +241,8 @@ 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))
} else {
copy_from_user_page(vma, page, addr,
buf, maddr + offset, bytes);
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