linux-kernel - i386 doublefault handler is broken with CONFIG_DEBUG

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-next>] [day] [month] [year] [list]

Date:	Thu, 09 Aug 2007 12:49:29 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>, Andi Kleen <ak@....de>
Subject: i386 doublefault handler is broken with CONFIG_DEBUG_SPINLOCK

The new percpu code has apparently broken the doublefault handler
when CONFIG_DEBUG_SPINLOCK is set. Doublefault is handled by
a hardware task, making the check

        SPIN_BUG_ON(lock->owner == current, lock, "recursion");

fault because it uses the FS register to access the percpu data
for current, and that register is zero in the new TSS. (The trace
I saw was on 2.6.20 where it was GS, but it looks like this will
still happen with FS on 2.6.22.)

Initializing FS in the doublefault_tss should fix it.

Signed-off-by: Chuck Ebbert <cebbert@...hat.com>

---

 NOTE: not even compile tested.

 arch/i386/kernel/doublefault.c |    1 +
 1 file changed, 1 insertion(+)

--- linux-2.6.22.noarch.orig/arch/i386/kernel/doublefault.c
+++ linux-2.6.22.noarch/arch/i386/kernel/doublefault.c
@@ -63,6 +63,7 @@ struct tss_struct doublefault_tss __cach
 		.cs		= __KERNEL_CS,
 		.ss		= __KERNEL_DS,
 		.ds		= __USER_DS,
+		.fs		= __KERNEL_PERCPU,

 		.__cr3		= __pa(swapper_pg_dir)
 	}
-
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/