Commit a5ec6ae1 authored Dec 18, 2017 by Jann Horn Committed by Daniel Borkmann Dec 21, 2017

bpf: force strict alignment checks for stack pointers



Force strict alignment checks for stack pointers because the tracking of
stack spills relies on it; unaligned stack accesses can lead to corruption
of spilled registers, which is exploitable.

Fixes: f1174f77 ("bpf/verifier: rework value tracking")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent ea25f914

kernel/bpf/verifier.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -1059,6 +1059,11 @@ static int check_ptr_alignment(struct bpf_verifier_env *env,
		break;
		case PTR_TO_STACK:
		pointer_desc = "stack ";
		/* The stack spill tracking logic in check_stack_write()
		* and check_stack_read() relies on stack accesses being
		* aligned.
		*/
		strict = true;
		break;
		default:
		break;