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: f1174f77b5 ("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>
This commit is contained in:
Jann Horn 2017-12-18 20:11:58 -08:00 committed by Daniel Borkmann
parent ea25f914dc
commit a5ec6ae161
1 changed files with 5 additions and 0 deletions

View File

@ -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;