On Mon, Jul 18, 2011 at 14:08 -0500, Matt Mackall wrote: > On Mon, 2011-07-18 at 22:39 +0400, Vasiliy Kulikov wrote: > > This patch implements 2 additional checks for the data copied from > > kernelspace to userspace and vice versa (original PAX_USERCOPY from PaX > > patch). Currently there are some very simple and cheap comparisons of > > supplied size and the size of a copied object known at the compile time > > in copy_* functions. This patch enhances these checks to check against > > stack frame boundaries and against SL*B object sizes. > > > > More precisely, it checks: > > > > 1) if the data touches the stack, checks whether it fully fits in the stack > > and whether it fully fits in a single stack frame. The latter is arch > > dependent, currently it is implemented for x86 with CONFIG_FRAME_POINTER=y > > only. It limits infoleaks/overwrites to a single frame and local variables > > only, and prevents saved return instruction pointer overwriting. > > > > 2) if the data is from the SL*B cache, checks whether it fully fits in a > > slab page and whether it overflows a slab object. E.g. if the memory > > was allocated as kmalloc(64, GFP_KERNEL) and one tries to copy 150 > > bytes, the copy would fail. > > FYI, this should almost certainly be split into (at least) two patches: > > - the stack check > - the SL*B check (probably one patch per allocator, preceded by one for > any shared infrastructure) Sure, also per architecture probably. But I want to get the comments about the feature itself before the division. Thanks, -- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>