bpf: check pending signals while verifying programs

[ Upstream commit c3494801cd1785e2c25f1a5735fa19ddcf9665da ]

Malicious user space may try to force the verifier to use as much cpu
time and memory as possible. Hence check for pending signals
while verifying the program.
Note that suspend of sys_bpf(PROG_LOAD) syscall will lead to EAGAIN,
since the kernel has to release the resources used for program verification.

Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1438b7396cb457bc116d42df7fabe758ee9251a0..335c00209f746fb003d6133413a67a5ec68297bc 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2919,6 +2919,9 @@ static int do_check(struct bpf_verifier_env *env)
                        goto process_bpf_exit;
                }
 
+               if (signal_pending(current))
+                       return -EAGAIN;
+
                if (need_resched())
                        cond_resched();