From: Alexei Starovoitov <ast@plumgrid.com>
Date: Tue, 14 Apr 2015 22:57:13 +0000 (-0700)
Subject: bpf: fix verifier memory corruption
X-Git-Tag: v3.18.13~24
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6ee16f4a033f21a9a41d60a8d93f9663ec269913;p=thirdparty%2Fkernel%2Fstable.git

bpf: fix verifier memory corruption

[ Upstream commit c3de6317d748e23b9e46ba36e10483728d00d144 ]

Due to missing bounds check the DAG pass of the BPF verifier can corrupt
the memory which can cause random crashes during program loading:

[8.449451] BUG: unable to handle kernel paging request at ffffffffffffffff
[8.451293] IP: [<ffffffff811de33d>] kmem_cache_alloc_trace+0x8d/0x2f0
[8.452329] Oops: 0000 [#1] SMP
[8.452329] Call Trace:
[8.452329]  [<ffffffff8116cc82>] bpf_check+0x852/0x2000
[8.452329]  [<ffffffff8116b7e4>] bpf_prog_load+0x1e4/0x310
[8.452329]  [<ffffffff811b190f>] ? might_fault+0x5f/0xb0
[8.452329]  [<ffffffff8116c206>] SyS_bpf+0x806/0xa30

Fixes: f1bca824dabb ("bpf: add search pruning optimization to verifier")
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
---

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9f81818f29418..d8dcc80472c1e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1324,7 +1324,8 @@ peek_stack:
 			/* tell verifier to check for equivalent states
 			 * after every call and jump
 			 */
-			env->explored_states[t + 1] = STATE_LIST_MARK;
+			if (t + 1 < insn_cnt)
+				env->explored_states[t + 1] = STATE_LIST_MARK;
 		} else {
 			/* conditional jump with two edges */
 			ret = push_insn(t, t + 1, FALLTHROUGH, env);