linux-kernel - [PATCH 1/1]: powerpc: block interrupts when updating TIDR

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: <20171201213140.GA2776@us.ibm.com>
Date:   Fri, 1 Dec 2017 13:31:40 -0800
From:   Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     clombard@...ux.vnet.ibm.com, felix@...ux.vnet.ibm.com,
        vaibhav@...ux.vnet.ibm.com, linuxppc-dev@...abs.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/1]: powerpc: block interrupts when updating TIDR

From: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Date: Tue, 28 Nov 2017 13:39:43 -0600
Subject: [PATCH 1/1]: powerpc: block interrupts when updating TIDR

clear_thread_tidr() is called in interrupt context as a part of delayed
put of the task structure (i.e as a part of timer interrupt). To prevent
a deadlock, block interrupts when holding vas_thread_id_lock to set/
clear TIDR for a task.

Signed-off-by: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
---
 arch/powerpc/kernel/process.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index bfdd783..aa8dbb9 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1509,14 +1509,15 @@ static int assign_thread_tidr(void)
 {
 	int index;
 	int err;
+	unsigned long flags;
 
 again:
 	if (!ida_pre_get(&vas_thread_ida, GFP_KERNEL))
 		return -ENOMEM;
 
-	spin_lock(&vas_thread_id_lock);
+	spin_lock_irqsave(&vas_thread_id_lock, flags);
 	err = ida_get_new_above(&vas_thread_ida, 1, &index);
-	spin_unlock(&vas_thread_id_lock);
+	spin_unlock_irqrestore(&vas_thread_id_lock, flags);
 
 	if (err == -EAGAIN)
 		goto again;
@@ -1524,9 +1525,9 @@ static int assign_thread_tidr(void)
 		return err;
 
 	if (index > MAX_THREAD_CONTEXT) {
-		spin_lock(&vas_thread_id_lock);
+		spin_lock_irqsave(&vas_thread_id_lock, flags);
 		ida_remove(&vas_thread_ida, index);
-		spin_unlock(&vas_thread_id_lock);
+		spin_unlock_irqrestore(&vas_thread_id_lock, flags);
 		return -ENOMEM;
 	}
 
@@ -1535,9 +1536,11 @@ static int assign_thread_tidr(void)
 
 static void free_thread_tidr(int id)
 {
-	spin_lock(&vas_thread_id_lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&vas_thread_id_lock, flags);
 	ida_remove(&vas_thread_ida, id);
-	spin_unlock(&vas_thread_id_lock);
+	spin_unlock_irqrestore(&vas_thread_id_lock, flags);
 }
 
 /*
-- 
2.7.4