[PATCH AUTOSEL 5.4 07/30] bpf: make sure skb->len != 0 when redirecting to a tunneling device

[PATCH AUTOSEL 5.4 07/30] bpf: make sure skb->len != 0 when redirecting to a tunneling device

[Sasha Levin]

From: Stanislav Fomichev <sdf@google.com>

[ Upstream commit 07ec7b502800ba9f7b8b15cb01dd6556bb41aaca ]

syzkaller managed to trigger another case where skb->len == 0
when we enter __dev_queue_xmit:

WARNING: CPU: 0 PID: 2470 at include/linux/skbuff.h:2576 skb_assert_len include/linux/skbuff.h:2576 [inline]
WARNING: CPU: 0 PID: 2470 at include/linux/skbuff.h:2576 __dev_queue_xmit+0x2069/0x35e0 net/core/dev.c:4295

Call Trace:
 dev_queue_xmit+0x17/0x20 net/core/dev.c:4406
 __bpf_tx_skb net/core/filter.c:2115 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2140 [inline]
 __bpf_redirect+0x5fb/0xda0 net/core/filter.c:2163
 ____bpf_clone_redirect net/core/filter.c:2447 [inline]
 bpf_clone_redirect+0x247/0x390 net/core/filter.c:2419
 bpf_prog_48159a89cb4a9a16+0x59/0x5e
 bpf_dispatcher_nop_func include/linux/bpf.h:897 [inline]
 __bpf_prog_run include/linux/filter.h:596 [inline]
 bpf_prog_run include/linux/filter.h:603 [inline]
 bpf_test_run+0x46c/0x890 net/bpf/test_run.c:402
 bpf_prog_test_run_skb+0xbdc/0x14c0 net/bpf/test_run.c:1170
 bpf_prog_test_run+0x345/0x3c0 kernel/bpf/syscall.c:3648
 __sys_bpf+0x43a/0x6c0 kernel/bpf/syscall.c:5005
 __do_sys_bpf kernel/bpf/syscall.c:5091 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5089 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5089
 do_syscall_64+0x54/0x70 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x61/0xc6

The reproducer doesn't really reproduce outside of syzkaller
environment, so I'm taking a guess here. It looks like we
do generate correct ETH_HLEN-sized packet, but we redirect
the packet to the tunneling device. Before we do so, we
__skb_pull l2 header and arrive again at skb->len == 0.
Doesn't seem like we can do anything better than having
an explicit check after __skb_pull?

Cc: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot+f635e86ec3fa0a37e019@syzkaller.appspotmail.com
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20221027225537.353077-1-sdf@google.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/core/filter.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index 72bf78032f45..49b31c2b4179 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2073,6 +2073,10 @@ static int __bpf_redirect_no_mac(struct sk_buff *skb, struct net_device *dev,
 
 	if (mlen) {
 		__skb_pull(skb, mlen);
+		if (unlikely(!skb->len)) {
+			kfree_skb(skb);
+			return -ERANGE;
+		}
 
 		/* At ingress, the mac header has already been pulled once.
 		 * At egress, skb_pospull_rcsum has to be done in case that
-- 
2.35.1

[PATCH AUTOSEL 5.4 21/30] ppp: associate skb with a device at tx

[Sasha Levin]

From: Stanislav Fomichev <sdf@google.com>

[ Upstream commit 9f225444467b98579cf28d94f4ad053460dfdb84 ]

Syzkaller triggered flow dissector warning with the following:

r0 = openat$ppp(0xffffffffffffff9c, &(0x7f0000000000), 0xc0802, 0x0)
ioctl$PPPIOCNEWUNIT(r0, 0xc004743e, &(0x7f00000000c0))
ioctl$PPPIOCSACTIVE(r0, 0x40107446, &(0x7f0000000240)={0x2, &(0x7f0000000180)=[{0x20, 0x0, 0x0, 0xfffff034}, {0x6}]})
pwritev(r0, &(0x7f0000000040)=[{&(0x7f0000000140)='\x00!', 0x2}], 0x1, 0x0, 0x0)

[    9.485814] WARNING: CPU: 3 PID: 329 at net/core/flow_dissector.c:1016 __skb_flow_dissect+0x1ee0/0x1fa0
[    9.485929]  skb_get_poff+0x53/0xa0
[    9.485937]  bpf_skb_get_pay_offset+0xe/0x20
[    9.485944]  ? ppp_send_frame+0xc2/0x5b0
[    9.485949]  ? _raw_spin_unlock_irqrestore+0x40/0x60
[    9.485958]  ? __ppp_xmit_process+0x7a/0xe0
[    9.485968]  ? ppp_xmit_process+0x5b/0xb0
[    9.485974]  ? ppp_write+0x12a/0x190
[    9.485981]  ? do_iter_write+0x18e/0x2d0
[    9.485987]  ? __import_iovec+0x30/0x130
[    9.485997]  ? do_pwritev+0x1b6/0x240
[    9.486016]  ? trace_hardirqs_on+0x47/0x50
[    9.486023]  ? __x64_sys_pwritev+0x24/0x30
[    9.486026]  ? do_syscall_64+0x3d/0x80
[    9.486031]  ? entry_SYSCALL_64_after_hwframe+0x63/0xcd

Flow dissector tries to find skb net namespace either via device
or via socket. Neigher is set in ppp_send_frame, so let's manually
use ppp->dev.

Cc: Paul Mackerras <paulus@samba.org>
Cc: linux-ppp@vger.kernel.org
Reported-by: syzbot+41cab52ab62ee99ed24a@syzkaller.appspotmail.com
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ppp/ppp_generic.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index a085213dc2ea..078c0f474f96 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -1522,6 +1522,8 @@ ppp_send_frame(struct ppp *ppp, struct sk_buff *skb)
 	int len;
 	unsigned char *cp;
 
+	skb->dev = ppp->dev;
+
 	if (proto < 0x8000) {
 #ifdef CONFIG_PPP_FILTER
 		/* check if we should pass this packet */
-- 
2.35.1

[PATCH AUTOSEL 5.4 22/30] bpf: Prevent decl_tag from being referenced in func_proto arg

[Sasha Levin]

From: Stanislav Fomichev <sdf@google.com>

[ Upstream commit f17472d4599697d701aa239b4c475a506bccfd19 ]

Syzkaller managed to hit another decl_tag issue:

  btf_func_proto_check kernel/bpf/btf.c:4506 [inline]
  btf_check_all_types kernel/bpf/btf.c:4734 [inline]
  btf_parse_type_sec+0x1175/0x1980 kernel/bpf/btf.c:4763
  btf_parse kernel/bpf/btf.c:5042 [inline]
  btf_new_fd+0x65a/0xb00 kernel/bpf/btf.c:6709
  bpf_btf_load+0x6f/0x90 kernel/bpf/syscall.c:4342
  __sys_bpf+0x50a/0x6c0 kernel/bpf/syscall.c:5034
  __do_sys_bpf kernel/bpf/syscall.c:5093 [inline]
  __se_sys_bpf kernel/bpf/syscall.c:5091 [inline]
  __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5091
  do_syscall_64+0x54/0x70 arch/x86/entry/common.c:48

This seems similar to commit ea68376c8bed ("bpf: prevent decl_tag from being
referenced in func_proto") but for the argument.

Reported-by: syzbot+8dd0551dda6020944c5d@syzkaller.appspotmail.com
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221123035422.872531-2-sdf@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/bpf/btf.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index a28bbec8c59f..8fd65a0eb7f3 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -2849,6 +2849,11 @@ static int btf_func_proto_check(struct btf_verifier_env *env,
 			break;
 		}
 
+		if (btf_type_is_resolve_source_only(arg_type)) {
+			btf_verifier_log_type(env, t, "Invalid arg#%u", i + 1);
+			return -EINVAL;
+		}
+
 		if (args[i].name_off &&
 		    (!btf_name_offset_valid(btf, args[i].name_off) ||
 		     !btf_name_valid_identifier(btf, args[i].name_off))) {
-- 
2.35.1