The error indicates that the verifier is letting through a program with a stack depth bigger than 512. This is due to the verifier not checking the stack depth after instruction rewrites are perfomed. For example, the MAY_GOTO instruction adds 8 bytes to the stack, which means that if the stack at the moment was already 512 bytes it would overflow after rewriting the instruction. The fix involves adding a stack depth check after all instruction rewrites are performed. Reported-by: syzbot+d2a2c639d03ac200a4f1@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Camila Alvarez <cam.alvarez.i@xxxxxxxxx> --- kernel/bpf/verifier.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 63749ad5ac6b..a9e23b6b8e8f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -21285,6 +21285,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3 if (ret == 0) ret = do_misc_fixups(env); + /* max stack depth verification must be done after rewrites as well */ + if (ret == 0) + ret = check_max_stack_depth(env); + /* do 32-bit optimization after insn patching has done so those patched * insns could be handled correctly. */ -- 2.34.1
