linux-kernel - [PATCH 3/4] debugfs: Add read-only/write-only size

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Date:	Mon, 12 Oct 2015 18:09:11 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: [PATCH 3/4] debugfs: Add read-only/write-only size_t file ops

There aren't any read-only or write-only size_t file ops, but there
is a caller of debugfs_create_size_t() that calls it with mode
equal to 0400. This leads to the possibility of userspace
modifying the file, so let's use the newly created
debugfs_create_mode() helper here to fix this.

Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
---
 fs/debugfs/file.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index f69d42efe4b8..e8e73aebe6b8 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -352,6 +352,8 @@ static int debugfs_size_t_get(void *data, u64 *val)
 }
 DEFINE_SIMPLE_ATTRIBUTE(fops_size_t, debugfs_size_t_get, debugfs_size_t_set,
 			"%llu\n");	/* %llu and %zu are more or less the same */
+DEFINE_SIMPLE_ATTRIBUTE(fops_size_t_ro, debugfs_size_t_get, NULL, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_size_t_wo, NULL, debugfs_size_t_set, "%llu\n");
 
 /**
  * debugfs_create_size_t - create a debugfs file that is used to read and write an size_t value
@@ -366,7 +368,8 @@ DEFINE_SIMPLE_ATTRIBUTE(fops_size_t, debugfs_size_t_get, debugfs_size_t_set,
 struct dentry *debugfs_create_size_t(const char *name, umode_t mode,
 				     struct dentry *parent, size_t *value)
 {
-	return debugfs_create_file(name, mode, parent, value, &fops_size_t);
+	return debugfs_create_mode(name, mode, parent, value, &fops_size_t,
+				   &fops_size_t_ro, &fops_size_t_wo);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_size_t);
 
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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