Bug 2395263 (CVE-2022-50253)

Summary: CVE-2022-50253 kernel: Linux kernel: Denial of Service in network packet redirection
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: low    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel's network packet processing. A local attacker with high privileges could trigger a denial of service. This occurs when a specially crafted network packet, after header removal, results in a zero-length packet being redirected to a tunneling device. The improper handling of this zero-length packet can lead to a kernel warning and system instability, causing the system to become unresponsive.
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Description OSIDB Bzimport 2025-09-15 15:04:06 UTC 
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?
Comment 1 Keith Grant 2025-09-15 19:07:41 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025091550-CVE-2022-50253-1ed7@gregkh/T