From: David Gibson Date: Wed, 30 Nov 2005 03:34:32 +0000 (-0800) Subject: [PATCH] Fix crash when ptrace poking hugepage areas X-Git-Tag: v2.6.15-rc4~4^2~9 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5bd0190bf3d7e53043a048e809ffa29d41b9d6ac;p=linux-2.6 [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 Acked-by: William Irwin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 17ee7e5a34..656476eedb 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -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); - set_page_dirty_lock(page); + if (!PageCompound(page)) + set_page_dirty_lock(page); } else { copy_from_user_page(vma, page, addr, buf, maddr + offset, bytes);