On Thu, Jun 25, 2015 at 10:59:57AM +0900, Sergey Senozhatsky wrote: > On (06/25/15 00:55), Seymour, Shane M wrote: > > Changed the documentation to allow sprintf() for small > > single values and explicitly say snprintf() must never be used in > > a show function to format data to be returned to user space. > > > > Change based on a discussion about the patch > > st: convert DRIVER_ATTR macros to DRIVER_ATTR_RO > > > > Suggested-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > Signed-off-by: Shane Seymour <shane.seymour@xxxxxx> > > --- > > --- a/Documentation/filesystems/sysfs.txt 2015-06-22 14:18:40.278620871 -0500 > > +++ b/Documentation/filesystems/sysfs.txt 2015-06-24 13:42:21.344446532 -0500 > > @@ -212,7 +212,9 @@ Other notes: > > - show() methods should return the number of bytes printed into the > > buffer. This is the return value of scnprintf(). > > > > -- show() should always use scnprintf(). > > +- show() must not use snprintf() when formatting a value to be > > + returned to user space. For small single values you can use > > + sprintf() otherwise you must use scnprintf(). > > Well, a single value can easily overflow > > sprintf(buf, "%s", dev->large_value); That's an obviously foolish sysfs attribute, if you do that, you deserve the kernel crash :) > Probably the wording better be "if you guarantee that overflow will > never happen, then you can use ...". For a document that no one has obviously read in the past 5 years, I really doubt we need to work too hard on the exact specific wording of it. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
