sysfs: fix problems with binary files

commit 4503efd0891c40e30928afb4b23dc3f99c62a6b2 upstream.

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>

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index 006fc64..aa24484 100644 (file)
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c
@@ -62,6 +62,9 @@ read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
        loff_t offs = *off;
        int count = min_t(size_t, bytes, PAGE_SIZE);
 
+       if (!bytes)
+               return 0;
+
        if (size) {
                if (offs > size)
                        return 0;
@@ -119,6 +122,9 @@ static ssize_t write(struct file *file, const char __user *userbuf,
        loff_t offs = *off;
        int count = min_t(size_t, bytes, PAGE_SIZE);
 
+       if (!bytes)
+               return 0;
+
        if (size) {
                if (offs > size)
                        return 0;