Bug 2521386 (CVE-2026-74646)

Summary: CVE-2026-74646 kernel: misc: fastrpc: take fl->lock when moving mmaps on interrupted invoke
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's fastrpc subsystem. When an invoke operation is interrupted by a signal, the `fastrpc_internal_invoke()` function moves memory mappings without properly holding the `fl->lock`. This missing lock during memory map manipulation creates a race condition, which could lead to memory corruption or system instability.
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Description OSIDB Bzimport 2026-08-22 15:42:59 UTC 
In the Linux kernel, the following vulnerability has been resolved:

misc: fastrpc: take fl->lock when moving mmaps on interrupted invoke

When an invoke is interrupted by a signal,
wait_for_completion_interruptible() returns -ERESTARTSYS and
fastrpc_internal_invoke() moves every buffer from fl->mmaps onto
cctx->invoke_interrupted_mmaps. This list_del()/list_add_tail() walk
runs without holding fl->lock, the lock that serialises fl->mmaps in
fastrpc_req_mmap() and fastrpc_req_munmap() everywhere else.

Take fl->lock around the move, matching every other fl->mmaps accessor.
Comment 1 gkamathe 2026-08-24 10:28:34 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082224-CVE-2026-74646-c5af@gregkh/T