linux-kernel - [PATCH RT 2/2 v2] list_bl: avoid BUG when the list is not locked

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]

Message-ID: <alpine.LRH.2.02.1911121110430.12815@file01.intranet.prod.int.rdu2.redhat.com>
Date:   Tue, 12 Nov 2019 11:16:29 -0500 (EST)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     tglx@...utronix.de, linux-rt-users@...r.kernel.org
cc:     Mike Snitzer <msnitzer@...hat.com>,
        Nikos Tsironis <ntsironis@...ikto.com>,
        Scott Wood <swood@...hat.com>,
        Ilias Tsitsimpis <iliastsi@...ikto.com>, dm-devel@...hat.com,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Daniel Wagner <dwagner@...e.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH RT 2/2 v2] list_bl: avoid BUG when the list is not locked

list_bl would crash with BUG() if we used it without locking. dm-snapshot 
uses its own locking on realtime kernels (it can't use list_bl because 
list_bl uses raw spinlock and dm-snapshot takes other non-raw spinlocks 
while holding bl_lock).

To avoid this BUG, we must set LIST_BL_LOCKMASK = 0.

This patch is intended only for the realtime kernel patchset, not for the 
upstream kernel.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>

Index: linux-rt-devel/include/linux/list_bl.h
===================================================================
--- linux-rt-devel.orig/include/linux/list_bl.h	2019-11-07 14:01:51.000000000 +0100
+++ linux-rt-devel/include/linux/list_bl.h	2019-11-08 10:12:49.000000000 +0100
@@ -19,7 +19,7 @@
  * some fast and compact auxiliary data.
  */
 
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+#if (defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)) && !defined(CONFIG_PREEMPT_RT_BASE)
 #define LIST_BL_LOCKMASK	1UL
 #else
 #define LIST_BL_LOCKMASK	0UL
@@ -161,9 +161,6 @@ static inline void hlist_bl_lock(struct
 	bit_spin_lock(0, (unsigned long *)b);
 #else
 	raw_spin_lock(&b->lock);
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
-	__set_bit(0, (unsigned long *)b);
-#endif
 #endif
 }
 
@@ -172,9 +169,6 @@ static inline void hlist_bl_unlock(struc
 #ifndef CONFIG_PREEMPT_RT_BASE
 	__bit_spin_unlock(0, (unsigned long *)b);
 #else
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
-	__clear_bit(0, (unsigned long *)b);
-#endif
 	raw_spin_unlock(&b->lock);
 #endif
 }