Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: x86/mm: Disable broadcast TLB flush when PCID is disabled Booting with "nopcid" clears X86_FEATURE_PCID and keeps CR4.PCIDE from being set to one. On AMD CPUs that support INVLPGB, broadcast TLB flushing remains enabled. There are two checks that decide whether the global ASID code runs, mm_global_asid() and consider_global_asid(), that key off of the X86_FEATURE_INVLPGB feature. Once an mm becomes active on more than three CPUs, consider_global_asid() assigns it a global ASID, after which flush_tlb_mm_range() takes the broadcast_tlb_flush() path using a non-zero PCID. Issuing an INVLPGB with a non-zero PCID while CR4.PCIDE is not set results in a #GP: Oops: general protection fault, kernel NULL pointer dereference 0x1: 0000 [#1] SMP NOPTI CPU: 158 UID: 0 PID: 3119 Comm: snap Not tainted 7.1.0-rc3 #1 PREEMPT(full) Hardware name: ... RIP: 0010:broadcast_tlb_flush Code: ... 89 da 48 83 c8 07 <0f> 01 fe eb 08 cc cc cc ... Call Trace: <TASK> flush_tlb_mm_range ptep_clear_flush wp_page_copy ? _raw_spin_unlock __handle_mm_fault handle_mm_fault do_user_addr_fault exc_page_fault asm_exc_page_fault All processors that support broadcast TLB invalidation also have PCID support, so it is only the "nopcid" scenario that is of concern. In this situation just disable the broadcast TLB support using the CPUID dependency support by making X86_FEATURE_INVLPGB dependent on X86_FEATURE_PCID. [ bp: Massage commit message. ]
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 4afeb0ed1753ebcad93ee3b45427ce85e9c8ec40 before fed725cace3ab1c4f7f8182e35029a603d953187; affected 4afeb0ed1753ebcad93ee3b45427ce85e9c8ec40 before d2d6d21286719b454d5d87a8758c23d2377d88a2; affected 4afeb0ed1753ebcad93ee3b45427ce85e9c8ec40 before 44126343d58c68adaa8343fbf1c07dd20078c35e |
| Linux / Linux | affected 6.15; unaffected 0 before 6.15; unaffected 6.18.35 through 6.18.*; unaffected 7.0.11 through 7.0.*; unaffected 7.1 through * |
CWE
No CWE identifiers supplied.