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/openbmc/linux/drivers/gpu/drm/i915/
H A Di915_vma.c1926a6b7 Mon Jun 20 07:36:59 CDT 2022 Thomas Hellström <thomas.hellstrom@linux.intel.com> drm/i915: Fix vm use-after-free in vma destruction

In vma destruction, the following race may occur:

Thread 1: Thread 2:
i915_vma_destroy();

...
list_del_init(vma->vm_link);
...
mutex_unlock(vma->vm->mutex);
__i915_vm_release();
release_references();

And in release_reference() we dereference vma->vm to get to the
vm gt pointer, leading to a use-after free.

However, __i915_vm_release() grabs the vm->mutex so the vm won't be
destroyed before vma->vm->mutex is released, so extract the gt pointer
under the vm->mutex to avoid the vma->vm dereference in
release_references().

v2: Fix a typo in the commit message (Andi Shyti)

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5944
Fixes: e1a7ab4fca0c ("drm/i915: Remove the vm open count")

Cc: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: Nirmoy Das <nirmoy.das@intel.con>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220620123659.381772-1-thomas.hellstrom@linux.intel.com