CVE-2025-38165: bpf, sockmap: Fix panic when calling skb_linearize
In the Linux kernel, the following vulnerability has been resolved:
bpf, sockmap: Fix panic when calling skblinearize
The panic can be reproduced by executing the command: ./bench sockmap -c 2 -p 1 -a --rx-verdict-ingress --rx-strp 100000
Then a kernel panic was captured: ''' [ 657.460555] kernel BUG at net/core/skbuff.c:2178! [ 657.462680] Tainted: [W]=WARN [ 657.463287] Workqueue: events skpsockbacklog ... [ 657.469610] <TASK> [ 657.469738] ? die+0x36/0x90 [ 657.469916] ? dotrap+0x1d0/0x270 [ 657.470118] ? pskbexpandhead+0x612/0xf40 [ 657.470376] ? pskbexpandhead+0x612/0xf40 [ 657.470620] ? doerrortrap+0xa3/0x170 [ 657.470846] ? pskbexpandhead+0x612/0xf40 [ 657.471092] ? handleinvalidop+0x2c/0x40 [ 657.471335] ? pskbexpandhead+0x612/0xf40 [ 657.471579] ? excinvalidop+0x2d/0x40 [ 657.471805] ? asmexcinvalidop+0x1a/0x20 [ 657.472052] ? pskbexpandhead+0xd1/0xf40 [ 657.472292] ? pskbexpandhead+0x612/0xf40 [ 657.472540] ? lockacquire+0x18f/0x4e0 [ 657.472766] ? findheldlock+0x2d/0x110 [ 657.472999] ? pfxpskbexpandhead+0x10/0x10 [ 657.473263] ? kmalloccachenoprof+0x5b/0x470 [ 657.473537] ? pfxlockrelease.isra.0+0x10/0x10 [ 657.473826] pskbpulltail+0xfd/0x1d20 [ 657.474062] ? kasanslaballoc+0x4e/0x90 [ 657.474707] skpsockskbingressenqueue+0x3bf/0x510 [ 657.475392] ? kasankmalloc+0xaa/0xb0 [ 657.476010] skpsockbacklog+0x5cf/0xd70 [ 657.476637] processonework+0x858/0x1a20 '''
The panic originates from the assertion BUGON(skbshared(skb)) in skblinearize(). A previous commit(see Fixes tag) introduced skbget() to avoid race conditions between skb operations in the backlog and skb release in the recvmsg path. However, this caused the panic to always occur when skblinearize is executed.
The "--rx-strp 100000" parameter forces the RX path to use the strparser module which aggregates data until it reaches 100KB before calling sockmap logic. The 100KB payload exceeds MAXMSGFRAGS, triggering skblinearize.
To fix this issue, just move skbget into skpsockskbingressenqueue.
''' skpsockbacklog: skpsockhandleskb skbget(skb) <== we move it into 'skpsockskbingressenqueue' skpsockskbingress ↓ | | → skpsockskbingressself | skpsockskbingressenqueue skpsockverdictapply↑ skblinearize '''
Note that for verdictapply path, the skbget operation is unnecessary so we add 'takeref' param to control it's behavior.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.113-1Fixed in 7.2.12-1Fixed in 7.2.13-1 - Compensating control
Move skb_get(skb) into sk_psock_skb_ingress_enqueue and use the take_ref parameter to avoid taking an unnecessary reference on the sk_psock_verdict_apply path.
Event History
Frequently Asked Questions
What is the severity of CVE-2025-38165?
CVE-2025-38165 has a high severity due to the potential for a kernel panic, which could disrupt system operations.
How do I fix CVE-2025-38165?
To mitigate CVE-2025-38165, update your Linux Kernel to the latest stable version where the vulnerability has been resolved.
What is the impact of CVE-2025-38165?
The impact of CVE-2025-38165 is that it may cause a kernel panic when specific sockmap configurations are utilized.
Which systems are affected by CVE-2025-38165?
CVE-2025-38165 affects systems running vulnerable versions of the Linux Kernel that use sockmap functionality.
What command can trigger the vulnerability in CVE-2025-38165?
The command './bench sockmap -c 2 -p 1 -a --rx-verdict-ingress --rx-strp 100000' can trigger the panic associated with CVE-2025-38165.