linux-kernel - [PATCH] kernel: initialize cpumask before parsing

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Message-Id: <20210401055823.3929-1-penguin-kernel@I-love.SAKURA.ne.jp>
Date:   Thu,  1 Apr 2021 14:58:23 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: [PATCH] kernel: initialize cpumask before parsing

KMSAN complains that new_value at cpumask_parse_user() from
write_irq_affinity() from irq_affinity_proc_write() is uninitialized.

  [  148.133411][ T5509] =====================================================
  [  148.135383][ T5509] BUG: KMSAN: uninit-value in find_next_bit+0x325/0x340
  [  148.137819][ T5509]
  [  148.138448][ T5509] Local variable ----new_value.i@..._affinity_proc_write created at:
  [  148.140768][ T5509]  irq_affinity_proc_write+0xc3/0x3d0
  [  148.142298][ T5509]  irq_affinity_proc_write+0xc3/0x3d0
  [  148.143823][ T5509] =====================================================

Since bitmap_parse() from cpumask_parse_user() calls find_next_bit(),
any alloc_cpumask_var() + cpumask_parse_user() sequence has possibility
that find_next_bit() accesses uninitialized cpu mask variable. Fix this
problem by replacing alloc_cpumask_var() with zalloc_cpumask_var().

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 kernel/irq/proc.c    | 4 ++--
 kernel/profile.c     | 2 +-
 kernel/trace/trace.c | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 98138788cb04..7c5cd42df3b9 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -144,7 +144,7 @@ static ssize_t write_irq_affinity(int type, struct file *file,
 	if (!irq_can_set_affinity_usr(irq) || no_irq_affinity)
 		return -EIO;
 
-	if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
+	if (!zalloc_cpumask_var(&new_value, GFP_KERNEL))
 		return -ENOMEM;
 
 	if (type)
@@ -238,7 +238,7 @@ static ssize_t default_affinity_write(struct file *file,
 	cpumask_var_t new_value;
 	int err;
 
-	if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
+	if (!zalloc_cpumask_var(&new_value, GFP_KERNEL))
 		return -ENOMEM;
 
 	err = cpumask_parse_user(buffer, count, new_value);
diff --git a/kernel/profile.c b/kernel/profile.c
index 6f69a4195d56..c2ebddb5e974 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -430,7 +430,7 @@ static ssize_t prof_cpu_mask_proc_write(struct file *file,
 	cpumask_var_t new_value;
 	int err;
 
-	if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
+	if (!zalloc_cpumask_var(&new_value, GFP_KERNEL))
 		return -ENOMEM;
 
 	err = cpumask_parse_user(buffer, count, new_value);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index eccb4e1187cc..7607dc8a20b2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4827,7 +4827,7 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
 	cpumask_var_t tracing_cpumask_new;
 	int err;
 
-	if (!alloc_cpumask_var(&tracing_cpumask_new, GFP_KERNEL))
+	if (!zalloc_cpumask_var(&tracing_cpumask_new, GFP_KERNEL))
 		return -ENOMEM;
 
 	err = cpumask_parse_user(ubuf, count, tracing_cpumask_new);
-- 
2.18.4