linux-kernel - BUG?: PAGE_FLAGS_CHECK_AT_PREP seems to be cleared too early (Was Re: I just got got another Oops

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 16 Mar 2009 17:03:59 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	"hugh@...itas.com" <hugh@...itas.com>
Cc:	Gene Heskett <gene.heskett@...il.com>,
	David Newall <davidn@...idnewall.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: BUG?: PAGE_FLAGS_CHECK_AT_PREP seems to be cleared too early (Was
 Re: I just got got another Oops

Hi,
I'm sorry if I miss something..

>From this patch
==
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=79f4b7bf393e67bbffec807cc68caaefc72b82ee
==
#define PAGE_FLAGS_CHECK_AT_PREP       ((1 << NR_PAGEFLAGS) - 1)
...
@@ -468,16 +467,16 @@ static inline int free_pages_check(struct page *page)
                (page_count(page) != 0)  |
                (page->flags & PAGE_FLAGS_CHECK_AT_FREE)))
....
+       if (PageReserved(page))
+               return 1;
+       if (page->flags & PAGE_FLAGS_CHECK_AT_PREP)
+               page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
+       return 0;
 }
==

PAGE_FLAGS_CHECK_AT_PREP is cleared by free_pages_check().

This means PG_head/PG_tail(PG_compound) flags are cleared here and Compound page
will never be freed in sane way.

Regards,
-Kame

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/