[PATCH v3 2/3] sysfs: Only accept read/write permissions for file attributes

From: Vivien Didelot
Date: Thu Mar 12 2015 - 09:59:59 EST


For sysfs file attributes, only read and write permissions make sense.
Mask provided attribute permissions accordingly and send a warning
to the console if invalid permission bits are set.

This patch is originally from Guenter [1] and includes the fixup
explained in the thread, that is printing permissions in octal format
and limiting the scope of attributes to SYSFS_PREALLOC | 0664.

[1] https://lkml.org/lkml/2015/1/19/599

Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Vivien Didelot <vivien.didelot@xxxxxxxxxxxxxxxxxxxx>
---
fs/sysfs/group.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
index 3fdccd9..b400c04 100644
--- a/fs/sysfs/group.c
+++ b/fs/sysfs/group.c
@@ -55,6 +55,12 @@ static int create_files(struct kernfs_node *parent, struct kobject *kobj,
if (!mode)
continue;
}
+
+ WARN(mode & ~(SYSFS_PREALLOC | 0664),
+ "Attribute %s: Invalid permissions 0%o\n",
+ (*attr)->name, mode);
+
+ mode &= SYSFS_PREALLOC | 0664;
error = sysfs_add_file_mode_ns(parent, *attr, false,
mode, NULL);
if (unlikely(error))
--
2.3.2

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