In the Linux kernel, the following vulnerability has been resolved:
bpf: make sure skb->len != 0 when redirecting to a tunneling device
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?
bpf: make sure skb->len != 0 when redirecting to a tunneling device
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?
Metrics
Affected Vendors & Products
No data.
No data.
No data.
No data.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Mon, 15 Sep 2025 14:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: make sure skb->len != 0 when redirecting to a tunneling device 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? | |
| Title | bpf: make sure skb->len != 0 when redirecting to a tunneling device | |
| References |
|
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-09-15T14:02:34.849Z
Reserved: 2025-09-15T13:58:00.973Z
Link: CVE-2022-50253
Vulnrichment
No data.
NVD
Status : Awaiting Analysis
Published: 2025-09-15T14:15:36.007
Modified: 2025-09-15T15:21:42.937
Link: CVE-2022-50253
Redhat
No data.
OpenCVE Enrichment
No data.