In the Linux kernel, the following vulnerability has been resolved:
riscv: Fix IPIs usage in kfenceprotectpage()
flushtlbkernel_range() may use IPIs to flush the TLBs of all the cores, which triggers the following warning when the irqs are disabled:
[ 3.455330] WARNING: CPU: 1 PID: 0 at kernel/smp.c:815 smpcallfunctionmanycond+0x452/0x520 [ 3.456647] Modules linked in: [ 3.457218] CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted 6.12.0-rc7-00010-g91d3de7240b8 #1 [ 3.457416] Hardware name: QEMU QEMU Virtual Machine, BIOS [ 3.457633] epc : smpcallfunctionmanycond+0x452/0x520 [ 3.457736] ra : oneachcpucondmask+0x1e/0x30 [ 3.457786] epc : ffffffff800b669a ra : ffffffff800b67c2 sp : ff2000000000bb50 [ 3.457824] gp : ffffffff815212b8 tp : ff6000008014f080 t0 : 000000000000003f [ 3.457859] t1 : ffffffff815221e0 t2 : 000000000000000f s0 : ff2000000000bc10 [ 3.457920] s1 : 0000000000000040 a0 : ffffffff815221e0 a1 : 0000000000000001 [ 3.457953] a2 : 0000000000010000 a3 : 0000000000000003 a4 : 0000000000000000 [ 3.458006] a5 : 0000000000000000 a6 : ffffffffffffffff a7 : 0000000000000000 [ 3.458042] s2 : ffffffff815223be s3 : 00fffffffffff000 s4 : ff600001ffe38fc0 [ 3.458076] s5 : ff600001ff950d00 s6 : 0000000200000120 s7 : 0000000000000001 [ 3.458109] s8 : 0000000000000001 s9 : ff60000080841ef0 s10: 0000000000000001 [ 3.458141] s11: ffffffff81524812 t3 : 0000000000000001 t4 : ff60000080092bc0 [ 3.458172] t5 : 0000000000000000 t6 : ff200000000236d0 [ 3.458203] status: 0000000200000100 badaddr: ffffffff800b669a cause: 0000000000000003 [ 3.458373] [<ffffffff800b669a>] smpcallfunctionmanycond+0x452/0x520 [ 3.458593] [<ffffffff800b67c2>] oneachcpucondmask+0x1e/0x30 [ 3.458625] [<ffffffff8000e4ca>] _flushtlbrange+0x118/0x1ca [ 3.458656] [<ffffffff8000e6b2>] flushtlbkernelrange+0x1e/0x26 [ 3.458683] [<ffffffff801ea56a>] kfenceprotect+0xc0/0xce [ 3.458717] [<ffffffff801e9456>] kfenceguardedfree+0xc6/0x1c0 [ 3.458742] [<ffffffff801e9d6c>] _kfencefree+0x62/0xc6 [ 3.458764] [<ffffffff801c57d8>] kfree+0x106/0x32c [ 3.458786] [<ffffffff80588cf2>] detachbufsplit+0x188/0x1a8 [ 3.458816] [<ffffffff8058708c>] virtqueuegetbufctx+0xb6/0x1f6 [ 3.458839] [<ffffffff805871da>] virtqueuegetbuf+0xe/0x16 [ 3.458880] [<ffffffff80613d6a>] virtblkdone+0x5c/0xe2 [ 3.458908] [<ffffffff8058766e>] vringinterrupt+0x6a/0x74 [ 3.458930] [<ffffffff800747d8>] _handleirqeventpercpu+0x7c/0xe2 [ 3.458956] [<ffffffff800748f0>] handleirqevent+0x3c/0x86 [ 3.458978] [<ffffffff800786cc>] handlesimpleirq+0x9e/0xbe [ 3.459004] [<ffffffff80073934>] generichandledomainirq+0x1c/0x2a [ 3.459027] [<ffffffff804bf87c>] imsichandleirq+0xba/0x120 [ 3.459056] [<ffffffff80073934>] generichandledomainirq+0x1c/0x2a [ 3.459080] [<ffffffff804bdb76>] riscvintcaiairq+0x24/0x34 [ 3.459103] [<ffffffff809d0452>] handleriscvirq+0x2e/0x4c [ 3.459133] [<ffffffff809d923e>] callonirqstack+0x32/0x40
So only flush the local TLB and let the lazy kfence page fault handling deal with the faults which could happen when a core has an old protected pte version cached in its TLB. That leads to potential inaccuracies which can be tolerated when using kfence.