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) -- Mathematics is the supreme nostalgia of our time. -- 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>