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authorRob Clark <robdclark@chromium.org>2023-01-19 20:32:58 +0300
committerRodrigo Vivi <rodrigo.vivi@intel.com>2023-01-30 23:48:08 +0300
commit41d419382ec7e257e54b7b6ff0d3623aafb1316d (patch)
treeb6cf4aff0a181e24eeb2994cfea2cd0c9c691cc0 /drivers
parent6d796c50f84ca79f1722bb131799e5a5710c4700 (diff)
downloadlinux-41d419382ec7e257e54b7b6ff0d3623aafb1316d.tar.xz
drm/i915: Avoid potential vm use-after-free
Adding the vm to the vm_xa table makes it visible to userspace, which could try to race with us to close the vm. So we need to take our extra reference before putting it in the table. Signed-off-by: Rob Clark <robdclark@chromium.org> Reviewed-by: Matthew Auld <matthew.auld@intel.com> Fixes: 9ec8795e7d91 ("drm/i915: Drop __rcu from gem_context->vm") Cc: <stable@vger.kernel.org> # v5.16+ Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20230119173321.2825472-1-robdclark@gmail.com (cherry picked from commit 99343c46d4e2b34c285d3d5f68ff04274c2f9fb4) Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/gpu/drm/i915/gem/i915_gem_context.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 6250de9b9196..e4b78ab4773b 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1861,11 +1861,19 @@ static int get_ppgtt(struct drm_i915_file_private *file_priv,
vm = ctx->vm;
GEM_BUG_ON(!vm);
+ /*
+ * Get a reference for the allocated handle. Once the handle is
+ * visible in the vm_xa table, userspace could try to close it
+ * from under our feet, so we need to hold the extra reference
+ * first.
+ */
+ i915_vm_get(vm);
+
err = xa_alloc(&file_priv->vm_xa, &id, vm, xa_limit_32b, GFP_KERNEL);
- if (err)
+ if (err) {
+ i915_vm_put(vm);
return err;
-
- i915_vm_get(vm);
+ }
GEM_BUG_ON(id == 0); /* reserved for invalid/unassigned ppgtt */
args->value = id;