UBUNTU-CVE-2026-53158: Null Pointer Dereference
In the Linux kernel, the following vulnerability has been resolved: misc: fastrpc: Fix NULL pointer dereference in rpmsg callback A NULL pointer dereference was observed on Hawi at boot when the DSP sends a glink message before fastrpcrpmsgprobe() has completed initialization: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000178 pc : rawspinlockirqsave+0x34/0x8c lr : fastrpcrpmsgcallback+0x3c/0xcc [fastrpc] ... Call trace: rawspinlockirqsave+0x34/0x8c (P) fastrpcrpmsgcallback+0x3c/0xcc [fastrpc] qcomglinknativerx+0x538/0x6a4 qcomglinksmemintr+0x14/0x24 [qcomglinksmem] The faulting address 0x178 corresponds to the lock variable inside struct fastrpcchannelctx, confirming that cctx is NULL when fastrpcrpmsgcallback() attempts to take the spinlock. There are two issues here. First, devsetdrvdata() is called before spinlockinit() and idrinit(), leaving a window where the callback can retrieve a valid cctx pointer but operate on an uninitialized spinlock. Second, the rpmsg channel becomes live as soon as the driver is bound, so fastrpcrpmsgcallback() can fire before devsetdrvdata() is called at all, resulting in devgetdrvdata() returning NULL. Fix both issues by moving all cctx initialization ahead of devsetdrvdata() so the structure is fully initialized before it becomes visible to the callback, and add a NULL check in fastrpcrpmsgcallback() as a guard against any remaining window.
Affected Software
Remediation
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-31.31.1 - Compensating control
Move all fastrpc cctx initialization, including spin_lock_init() and idr_init(), before dev_set_drvdata() so the structure is fully initialized before it becomes visible to the callback.
- Compensating control
Add a NULL check for cctx in fastrpc_rpmsg_callback() before attempting to take its spinlock.
Event History
Frequently Asked Questions
Which Ubuntu kernel package families are listed as affected?
The listed package families are linux, linux-aws, linux-azure, linux-azure-fde, linux-gcp, linux-oracle, linux-raspi, and linux-realtime.
What conditions trigger the failure?
The failure can occur during driver initialization when the DSP sends a GLINK/RPMSG message before fastrpc_rpmsg_probe() has completed. The RPMSG channel may become live before driver data, the spinlock, and the IDR are fully initialized.
What access and impact does the severity vector indicate?
The CVSS vector indicates that exploitation requires local access and low privileges, with no user interaction required. The stated impact is limited to availability, with high availability impact and no confidentiality or integrity impact.
How might an affected system present the issue?
The reported symptom is a kernel NULL pointer dereference at boot in fastrpc_rpmsg_callback(), with a call trace involving _raw_spin_lock_irqsave, qcom_glink_native_rx, and qcom_glink_smem_intr. The NULL channel-context pointer causes the callback to access the lock field at address 0x178.