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Subject[PATCH 4.10 062/110] drm/i915/kvmgt: fix suspicious rcu dereference usage
Date
4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Changbin Du <changbin.du@intel.com>

commit 5180edc2421117766fcb9c2d2dc6bfaeefdeb709 upstream.

The srcu read lock must be held while accessing kvm memslots.
This patch fix below warning for function kvmgt_rw_gpa().

[ 165.345093] [ ERR: suspicious RCU usage. ]
[ 165.416538] Call Trace:
[ 165.418989] dump_stack+0x85/0xc2
[ 165.422310] lockdep_rcu_suspicious+0xd7/0x110
[ 165.426769] kvm_read_guest_page+0x195/0x1b0 [kvm]
[ 165.431574] kvm_read_guest+0x50/0x90 [kvm]
[ 165.440492] kvmgt_rw_gpa+0x43/0xa0 [kvmgt]
[ 165.444683] kvmgt_read_gpa+0x11/0x20 [kvmgt]
[ 165.449061] gtt_get_entry64+0x4d/0xc0 [i915]
[ 165.453438] ppgtt_populate_shadow_page_by_guest_entry+0x380/0xdc0 [i915]
[ 165.460254] shadow_mm+0xd1/0x460 [i915]
[ 165.472488] intel_vgpu_create_mm+0x1ab/0x210 [i915]
[ 165.477472] intel_vgpu_g2v_create_ppgtt_mm+0x5f/0xc0 [i915]
[ 165.483154] pvinfo_mmio_write+0x19b/0x1d0 [i915]
[ 165.499068] intel_vgpu_emulate_mmio_write+0x3f9/0x600 [i915]
[ 165.504827] intel_vgpu_rw+0x114/0x150 [kvmgt]
[ 165.509281] intel_vgpu_write+0x16f/0x1a0 [kvmgt]
[ 165.513993] vfio_mdev_write+0x20/0x30 [vfio_mdev]
[ 165.518793] vfio_device_fops_write+0x24/0x30 [vfio]
[ 165.523770] __vfs_write+0x28/0x120
[ 165.540529] vfs_write+0xce/0x1f0

v2: fix Cc format for stable

Signed-off-by: Changbin Du <changbin.du@intel.com>
Reviewed-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: Jike Song <jike.song@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/i915/gvt/kvmgt.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1422,7 +1422,7 @@ static int kvmgt_rw_gpa(unsigned long ha
{
struct kvmgt_guest_info *info;
struct kvm *kvm;
- int ret;
+ int idx, ret;
bool kthread = current->mm == NULL;

if (!handle_valid(handle))
@@ -1434,8 +1434,10 @@ static int kvmgt_rw_gpa(unsigned long ha
if (kthread)
use_mm(kvm->mm);

+ idx = srcu_read_lock(&kvm->srcu);
ret = write ? kvm_write_guest(kvm, gpa, buf, len) :
kvm_read_guest(kvm, gpa, buf, len);
+ srcu_read_unlock(&kvm->srcu, idx);

if (kthread)
unuse_mm(kvm->mm);

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