From a1ac5f0943019bfd76345fe05a42cbc400da685c Mon Sep 17 00:00:00 2001 From: Weinan Li Date: Mon, 17 Sep 2018 09:46:14 +0800 Subject: [PATCH] drm/i915/gvt: request srcu_read_lock before checking if one gfn is valid Fix the suspicious RCU usage issue in intel_vgpu_emulate_mmio_write. Here need to request the srcu read lock of kvm->srcu before doing gfn_to_memslot(). The detailed log is as below: [ 218.710688] ============================= [ 218.710690] WARNING: suspicious RCU usage [ 218.710693] 4.14.15-dd+ #314 Tainted: G U [ 218.710695] ----------------------------- [ 218.710697] ./include/linux/kvm_host.h:575 suspicious rcu_dereference_check() usage! [ 218.710699] other info that might help us debug this: [ 218.710702] rcu_scheduler_active = 2, debug_locks = 1 [ 218.710704] 1 lock held by qemu-system-x86/2144: [ 218.710706] #0: (&gvt->lock){+.+.}, at: [] intel_vgpu_emulate_mmio_write+0x5a/0x2d0 [ 218.710721] stack backtrace: [ 218.710724] CPU: 0 PID: 2144 Comm: qemu-system-x86 Tainted: G U 4.14.15-dd+ #314 [ 218.710727] Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.1.1 10/07/2015 [ 218.710729] Call Trace: [ 218.710734] dump_stack+0x7c/0xb3 [ 218.710739] gfn_to_memslot+0x15f/0x170 [ 218.710743] kvm_is_visible_gfn+0xa/0x30 [ 218.710746] intel_vgpu_emulate_gtt_mmio_write+0x267/0x3c0 [ 218.710751] ? __mutex_unlock_slowpath+0x3b/0x260 [ 218.710754] intel_vgpu_emulate_mmio_write+0x182/0x2d0 [ 218.710759] intel_vgpu_rw+0xba/0x170 [kvmgt] [ 218.710763] intel_vgpu_write+0x14d/0x1a0 [kvmgt] [ 218.710767] __vfs_write+0x23/0x130 [ 218.710770] vfs_write+0xb0/0x1b0 [ 218.710774] SyS_pwrite64+0x73/0x90 [ 218.710777] entry_SYSCALL_64_fastpath+0x25/0x9c [ 218.710780] RIP: 0033:0x7f33e8a91da3 [ 218.710783] RSP: 002b:00007f33dddc8700 EFLAGS: 00000293 v2: add 'Fixes' tag, refine log format.(Zhenyu) Fixes: cc753fbe1ac4 ("drm/i915/gvt: validate gfn before set shadow page") Reviewed-by: Zhenyu Wang Signed-off-by: Weinan Li Signed-off-by: Zhenyu Wang --- drivers/gpu/drm/i915/gvt/kvmgt.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c index c7afee37b2b8..9ad89e38f6c0 100644 --- a/drivers/gpu/drm/i915/gvt/kvmgt.c +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c @@ -1833,6 +1833,8 @@ static bool kvmgt_is_valid_gfn(unsigned long handle, unsigned long gfn) { struct kvmgt_guest_info *info; struct kvm *kvm; + int idx; + bool ret; if (!handle_valid(handle)) return false; @@ -1840,8 +1842,11 @@ static bool kvmgt_is_valid_gfn(unsigned long handle, unsigned long gfn) info = (struct kvmgt_guest_info *)handle; kvm = info->kvm; - return kvm_is_visible_gfn(kvm, gfn); + idx = srcu_read_lock(&kvm->srcu); + ret = kvm_is_visible_gfn(kvm, gfn); + srcu_read_unlock(&kvm->srcu, idx); + return ret; } struct intel_gvt_mpt kvmgt_mpt = { -- 2.30.2