On Thu, Nov 22, 2012 at 01:24:10PM +0200, Artem Bityutskiy wrote: > On Thu, 2012-11-22 at 14:14 +0300, Dan Carpenter wrote: > > On Thu, Nov 22, 2012 at 12:31:37PM +0200, Artem Bityutskiy wrote: > > > On Sat, 2012-11-17 at 18:11 +0300, Dan Carpenter wrote: > > > > out_len = le32_to_cpu(dn->size); > > > > - buf = kmalloc(out_len * WORST_COMPR_FACTOR, GFP_NOFS); > > > > + buf = kmalloc_array(out_len, WORST_COMPR_FACTOR, GFP_NOFS); > > > > if (!buf) > > > > return -ENOMEM; > > > > > > I think this makes the code unreadable, because we really allocate a > > > buffer, not an array. > > > > The problem with the original code is that the multiply looks very > > suspect. Everyone who reads it has to backtrack to find where > > dn->size is capped. > > > > I guess in one sense we never allocate an array, we always declare > > it on the stack. We debated the naming and there really isn't a > > good name. kmalloc_safe() isn't right either. But anyway, the > > intent is that eventually someone will right a coccinelle script > > which replaces all these allocations with kmalloc_array(). > > > > When I look at this code more, I still don't see a place where > > dn->size is capped. So I think we *need* the integer overflow > > check as an integer overflow fix and not just as a cleanup. > > It is validated in fs/ubifs/io.c in 'ubifs_check_node()'. > > 'dn' stands for 'direntry node'. We read it from the media and validate > it immediately after we've read it, including 'dn->len'. > > The entire code is written with the following assumption that whatever > is read from the flash media is validated. It's actually dn->size that we care about here. That's not checked in ubifs_check_node(). :( It may be checked somewhere else, I'm still looking. regards, dan cparenter -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
