• Miao Xie's avatar
    sysfs: fix off-by-one error in fill_read_buffer() · 8118a859
    Miao Xie authored
    I found that there is a off-by-one problem in the following code.
    
    Version:	2.6.24-rc2
    File:		fs/sysfs/file.c:118-122
    Function:	fill_read_buffer
    --------------------------------------------------------------------
    	count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
    
    	sysfs_put_active_two(attr_sd);
    
    	BUG_ON(count > (ssize_t)PAGE_SIZE);
    --------------------------------------------------------------------
    
    Because according to the specification of the sysfs and the implement of
    the show methods, the show methods return the number of bytes which would
    be generated for the given input, excluding the trailing null.So if the
    return value of the show methods equals PAGE_SIZE - 1, the buffer is full
    in fact.  And if the return value equals PAGE_SIZE, the resulting string
    was already truncated,or buffer overflow occurred.
    
    This patch fixes an off-by-one error in fill_read_buffer.
    Signed-off-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Acked-by: default avatarTejun Heo <teheo@suse.de>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
    8118a859
file.c 18.2 KB