sysfs: fix problems with binary files

Some sysfs binary files don't like having 0 passed to them as a size.
Fix this up at the root by just returning to the vfs if userspace asks
us for a zero sized buffer.

Thanks to Pavel Roskin for pointing this out.

Reported-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index 66f6e58a7e4b..f2c478c3424e 100644
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c
@@ -63,6 +63,9 @@ read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
         int count = min_t(size_t, bytes, PAGE_SIZE);
         char *temp;
 
+        if (!bytes)
+                return 0;
+
         if (size) {
                 if (offs > size)
                         return 0;
@@ -131,6 +134,9 @@ static ssize_t write(struct file *file, const char __user *userbuf,
         int count = min_t(size_t, bytes, PAGE_SIZE);
         char *temp;
 
+        if (!bytes)
+                return 0;
+
         if (size) {
                 if (offs > size)
                         return 0;