In the Linux kernel, the following vulnerability has been resolved:
powerpc64/bpf: Limit 'ldbrx' to processors compliant with ISA v2.06
Johan reported the below crash with test_bpf on ppc64 e5500:
testbpf: #296 ALUENDFROMLE 64: 0x0123456789abcdef -> 0x67452301 jited:1 Oops: Exception in kernel mode, sig: 4 [#1] BE PAGESIZE=4K SMP NRCPUS=24 QEMU e500 Modules linked in: testbpf(+) CPU: 0 PID: 76 Comm: insmod Not tainted 5.14.0-03771-g98c2059e008a-dirty #1 NIP: 8000000000061c3c LR: 80000000006dea64 CTR: 8000000000061c18 REGS: c0000000032d3420 TRAP: 0700 Not tainted (5.14.0-03771-g98c2059e008a-dirty) MSR: 0000000080089000 <EE,ME> CR: 88002822 XER: 20000000 IRQMASK: 0 <...> NIP [8000000000061c3c] 0x8000000000061c3c LR [80000000006dea64] .runone+0x104/0x17c [testbpf] Call Trace: .runone+0x60/0x17c [testbpf] (unreliable) .testbpfinit+0x6a8/0xdc8 [testbpf] .dooneinitcall+0x6c/0x28c .doinitmodule+0x68/0x28c .loadmodule+0x2460/0x2abc .dosysinitmodule+0x120/0x18c .systemcallexception+0x110/0x1b8 systemcallcommon+0xf0/0x210 --- interrupt: c00 at 0x101d0acc <...> ---[ end trace 47b2bf19090bb3d0 ]---
Illegal instruction
The illegal instruction turned out to be 'ldbrx' emitted for BPFFROM[L|B]E, which was only introduced in ISA v2.06. Guard use of the same and implement an alternative approach for older processors.