linux-kernel - [PATCH V2 09/10] kasan: Prevent deadlock in kasan reporting

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Date:	Wed, 26 Aug 2015 13:56:17 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
	ryabinin.a.a@...il.com
Cc:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH V2 09/10] kasan: Prevent deadlock in kasan reporting

We we end up calling kasan_report in real mode, our shadow mapping
for even spinlock variable will show poisoned. This will result
in us calling kasan_report_error with lock_report spin lock held.
To prevent this disable kasan reporting when we are priting
error w.r.t kasan.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
 mm/kasan/report.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 79fbc5d14bd2..82b41eb83e43 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -185,6 +185,10 @@ void kasan_report_error(struct kasan_access_info *info)
 {
 	unsigned long flags;
 
+	/*
+	 * Make sure we don't end up in loop.
+	 */
+	kasan_disable_current();
 	spin_lock_irqsave(&report_lock, flags);
 	pr_err("================================="
 		"=================================\n");
@@ -194,12 +198,17 @@ void kasan_report_error(struct kasan_access_info *info)
 	pr_err("================================="
 		"=================================\n");
 	spin_unlock_irqrestore(&report_lock, flags);
+	kasan_enable_current();
 }
 
 void kasan_report_user_access(struct kasan_access_info *info)
 {
 	unsigned long flags;
 
+	/*
+	 * Make sure we don't end up in loop.
+	 */
+	kasan_disable_current();
 	spin_lock_irqsave(&report_lock, flags);
 	pr_err("================================="
 		"=================================\n");
@@ -212,6 +221,7 @@ void kasan_report_user_access(struct kasan_access_info *info)
 	pr_err("================================="
 		"=================================\n");
 	spin_unlock_irqrestore(&report_lock, flags);
+	kasan_enable_current();
 }
 
 void kasan_report(unsigned long addr, size_t size,
-- 
2.5.0

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