Josef Bacik 484611357c bpf: allow access into map value arrays ... Suppose you have a map array value that is something like this struct foo { unsigned iter; int array[SOME_CONSTANT]; }; You can easily insert this into an array, but you cannot modify the contents of foo->array[] after the fact. This is because we have no way to verify we won't go off the end of the array at verification time. This patch provides a start for this work. We accomplish this by keeping track of a minimum and maximum value a register could be while we're checking the code. Then at the time we try to do an access into a MAP_VALUE we verify that the maximum offset into that region is a valid access into that memory region. So in practice, code such as this unsigned index = 0; if (foo->iter >= SOME_CONSTANT) foo->iter = index; else index = foo->iter++; foo->array[index] = bar; would be allowed, as we can verify that index will always be between 0 and SOME_CONSTANT-1. If you wish to use signed values you'll have to have an extra check to make sure the index isn't less than 0, or do something like index %= SOME_CONSTANT. Signed-off-by: Josef Bacik <jbacik@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>		2016-09-29 01:35:35 -04:00
..
arraymap.c
core.c	bpf: clean up put_cpu_var usage	2016-09-27 22:09:17 -04:00
hashtab.c
helpers.c
inode.c
Makefile
percpu_freelist.c
percpu_freelist.h
stackmap.c
syscall.c
verifier.c	bpf: allow access into map value arrays	2016-09-29 01:35:35 -04:00