Bug 2492737 (CVE-2026-53158)

Summary: CVE-2026-53158 kernel: misc: fastrpc: Fix NULL pointer dereference in rpmsg callback
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Priority: unspecified    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the Linux kernel's fastrpc component. This vulnerability occurs due to a NULL pointer dereference when the Digital Signal Processor (DSP) sends a glink message before the fastrpc driver is fully initialized. This can lead to system instability or a denial of service (DoS) condition, as the kernel attempts to access uninitialized memory during an rpmsg callback.
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Description OSIDB Bzimport 2026-06-25 10:03:06 UTC 
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 fastrpc_rpmsg_probe() has completed
initialization:

  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000178
  pc : _raw_spin_lock_irqsave+0x34/0x8c
  lr : fastrpc_rpmsg_callback+0x3c/0xcc [fastrpc]
  ...
  Call trace:
   _raw_spin_lock_irqsave+0x34/0x8c (P)
   fastrpc_rpmsg_callback+0x3c/0xcc [fastrpc]
   qcom_glink_native_rx+0x538/0x6a4
   qcom_glink_smem_intr+0x14/0x24 [qcom_glink_smem]

The faulting address 0x178 corresponds to the lock variable inside
struct fastrpc_channel_ctx, confirming that cctx is NULL when
fastrpc_rpmsg_callback() attempts to take the spinlock.

There are two issues here. First, dev_set_drvdata() is called before
spin_lock_init() and idr_init(), 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 fastrpc_rpmsg_callback() can fire before dev_set_drvdata()
is called at all, resulting in dev_get_drvdata() returning NULL.

Fix both issues by moving all cctx initialization ahead of
dev_set_drvdata() so the structure is fully initialized before it
becomes visible to the callback, and add a NULL check in
fastrpc_rpmsg_callback() as a guard against any remaining window.
Comment 1 TEJ RATHI 2026-06-26 08:58:17 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062549-CVE-2026-53158-332e@gregkh/T