On Mon, Jan 16, 2017 at 2:23 AM, Michael Ellerman <m...@ellerman.id.au> wrote: > Arnd Bergmann <a...@arndb.de> writes: > >> After the latest change to make sure the compiler actually does a memset, >> it is now smart enough to flag the stack overflow at compile time, >> at least with gcc-7.0: >> >> drivers/misc/lkdtm_bugs.c: In function 'lkdtm_CORRUPT_STACK': >> drivers/misc/lkdtm_bugs.c:88:144: warning: 'memset' writing 64 bytes into a >> region of size 8 overflows the destination [-Wstringop-overflow=] >> >> To outsmart the compiler again, this moves the memset into a noinline >> function where (for now) it doesn't see that we intentionally write >> broken code here. > > Heh, darn it. > > I suspect this is an arms race we are eventually going to lose. At some > point we might have to switch to writing some of these in asm :/
Yeah, though I'm going to keep trying to avoid this as much as possible. I was almost there when building the .rodata execution test, but I found horrible tricks. :P -Kees -- Kees Cook Nexus Security
