--- /dev/null
+From 0e45882ca829b26b915162e8e86dbb1095768e9e Mon Sep 17 00:00:00 2001
+From: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
+Date: Tue, 5 Mar 2024 15:35:06 +0100
+Subject: drm/i915/vma: Fix UAF on destroy against retire race
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+From: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
+
+commit 0e45882ca829b26b915162e8e86dbb1095768e9e upstream.
+
+Object debugging tools were sporadically reporting illegal attempts to
+free a still active i915 VMA object when parking a GT believed to be idle.
+
+[161.359441] ODEBUG: free active (active state 0) object: ffff88811643b958 object type: i915_active hint: __i915_vma_active+0x0/0x50 [i915]
+[161.360082] WARNING: CPU: 5 PID: 276 at lib/debugobjects.c:514 debug_print_object+0x80/0xb0
+...
+[161.360304] CPU: 5 PID: 276 Comm: kworker/5:2 Not tainted 6.5.0-rc1-CI_DRM_13375-g003f860e5577+ #1
+[161.360314] Hardware name: Intel Corporation Rocket Lake Client Platform/RocketLake S UDIMM 6L RVP, BIOS RKLSFWI1.R00.3173.A03.2204210138 04/21/2022
+[161.360322] Workqueue: i915-unordered __intel_wakeref_put_work [i915]
+[161.360592] RIP: 0010:debug_print_object+0x80/0xb0
+...
+[161.361347] debug_object_free+0xeb/0x110
+[161.361362] i915_active_fini+0x14/0x130 [i915]
+[161.361866] release_references+0xfe/0x1f0 [i915]
+[161.362543] i915_vma_parked+0x1db/0x380 [i915]
+[161.363129] __gt_park+0x121/0x230 [i915]
+[161.363515] ____intel_wakeref_put_last+0x1f/0x70 [i915]
+
+That has been tracked down to be happening when another thread is
+deactivating the VMA inside __active_retire() helper, after the VMA's
+active counter has been already decremented to 0, but before deactivation
+of the VMA's object is reported to the object debugging tool.
+
+We could prevent from that race by serializing i915_active_fini() with
+__active_retire() via ref->tree_lock, but that wouldn't stop the VMA from
+being used, e.g. from __i915_vma_retire() called at the end of
+__active_retire(), after that VMA has been already freed by a concurrent
+i915_vma_destroy() on return from the i915_active_fini(). Then, we should
+rather fix the issue at the VMA level, not in i915_active.
+
+Since __i915_vma_parked() is called from __gt_park() on last put of the
+GT's wakeref, the issue could be addressed by holding the GT wakeref long
+enough for __active_retire() to complete before that wakeref is released
+and the GT parked.
+
+I believe the issue was introduced by commit d93939730347 ("drm/i915:
+Remove the vma refcount") which moved a call to i915_active_fini() from
+a dropped i915_vma_release(), called on last put of the removed VMA kref,
+to i915_vma_parked() processing path called on last put of a GT wakeref.
+However, its visibility to the object debugging tool was suppressed by a
+bug in i915_active that was fixed two weeks later with commit e92eb246feb9
+("drm/i915/active: Fix missing debug object activation").
+
+A VMA associated with a request doesn't acquire a GT wakeref by itself.
+Instead, it depends on a wakeref held directly by the request's active
+intel_context for a GT associated with its VM, and indirectly on that
+intel_context's engine wakeref if the engine belongs to the same GT as the
+VMA's VM. Those wakerefs are released asynchronously to VMA deactivation.
+
+Fix the issue by getting a wakeref for the VMA's GT when activating it,
+and putting that wakeref only after the VMA is deactivated. However,
+exclude global GTT from that processing path, otherwise the GPU never goes
+idle. Since __i915_vma_retire() may be called from atomic contexts, use
+async variant of wakeref put. Also, to avoid circular locking dependency,
+take care of acquiring the wakeref before VM mutex when both are needed.
+
+v7: Add inline comments with justifications for:
+ - using untracked variants of intel_gt_pm_get/put() (Nirmoy),
+ - using async variant of _put(),
+ - not getting the wakeref in case of a global GTT,
+ - always getting the first wakeref outside vm->mutex.
+v6: Since __i915_vma_active/retire() callbacks are not serialized, storing
+ a wakeref tracking handle inside struct i915_vma is not safe, and
+ there is no other good place for that. Use untracked variants of
+ intel_gt_pm_get/put_async().
+v5: Replace "tile" with "GT" across commit description (Rodrigo),
+ - avoid mentioning multi-GT case in commit description (Rodrigo),
+ - explain why we need to take a temporary wakeref unconditionally inside
+ i915_vma_pin_ww() (Rodrigo).
+v4: Refresh on top of commit 5e4e06e4087e ("drm/i915: Track gt pm
+ wakerefs") (Andi),
+ - for more easy backporting, split out removal of former insufficient
+ workarounds and move them to separate patches (Nirmoy).
+ - clean up commit message and description a bit.
+v3: Identify root cause more precisely, and a commit to blame,
+ - identify and drop former workarounds,
+ - update commit message and description.
+v2: Get the wakeref before VM mutex to avoid circular locking dependency,
+ - drop questionable Fixes: tag.
+
+Fixes: d93939730347 ("drm/i915: Remove the vma refcount")
+Closes: https://gitlab.freedesktop.org/drm/intel/issues/8875
+Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
+Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
+Cc: Nirmoy Das <nirmoy.das@intel.com>
+Cc: Andi Shyti <andi.shyti@linux.intel.com>
+Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
+Cc: stable@vger.kernel.org # v5.19+
+Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
+Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
+Link: https://patchwork.freedesktop.org/patch/msgid/20240305143747.335367-6-janusz.krzysztofik@linux.intel.com
+(cherry picked from commit f3c71b2ded5c4367144a810ef25f998fd1d6c381)
+Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
+Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/gpu/drm/i915/i915_vma.c | 42 +++++++++++++++++++++++++++++++++-------
+ 1 file changed, 35 insertions(+), 7 deletions(-)
+
+--- a/drivers/gpu/drm/i915/i915_vma.c
++++ b/drivers/gpu/drm/i915/i915_vma.c
+@@ -33,6 +33,7 @@
+ #include "gt/intel_engine.h"
+ #include "gt/intel_engine_heartbeat.h"
+ #include "gt/intel_gt.h"
++#include "gt/intel_gt_pm.h"
+ #include "gt/intel_gt_requests.h"
+ #include "gt/intel_tlb.h"
+
+@@ -102,12 +103,34 @@ static inline struct i915_vma *active_to
+
+ static int __i915_vma_active(struct i915_active *ref)
+ {
+- return i915_vma_tryget(active_to_vma(ref)) ? 0 : -ENOENT;
++ struct i915_vma *vma = active_to_vma(ref);
++
++ if (!i915_vma_tryget(vma))
++ return -ENOENT;
++
++ /*
++ * Exclude global GTT VMA from holding a GT wakeref
++ * while active, otherwise GPU never goes idle.
++ */
++ if (!i915_vma_is_ggtt(vma))
++ intel_gt_pm_get(vma->vm->gt);
++
++ return 0;
+ }
+
+ static void __i915_vma_retire(struct i915_active *ref)
+ {
+- i915_vma_put(active_to_vma(ref));
++ struct i915_vma *vma = active_to_vma(ref);
++
++ if (!i915_vma_is_ggtt(vma)) {
++ /*
++ * Since we can be called from atomic contexts,
++ * use an async variant of intel_gt_pm_put().
++ */
++ intel_gt_pm_put_async(vma->vm->gt);
++ }
++
++ i915_vma_put(vma);
+ }
+
+ static struct i915_vma *
+@@ -1403,7 +1426,7 @@ int i915_vma_pin_ww(struct i915_vma *vma
+ struct i915_vma_work *work = NULL;
+ struct dma_fence *moving = NULL;
+ struct i915_vma_resource *vma_res = NULL;
+- intel_wakeref_t wakeref = 0;
++ intel_wakeref_t wakeref;
+ unsigned int bound;
+ int err;
+
+@@ -1423,8 +1446,14 @@ int i915_vma_pin_ww(struct i915_vma *vma
+ if (err)
+ return err;
+
+- if (flags & PIN_GLOBAL)
+- wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm);
++ /*
++ * In case of a global GTT, we must hold a runtime-pm wakeref
++ * while global PTEs are updated. In other cases, we hold
++ * the rpm reference while the VMA is active. Since runtime
++ * resume may require allocations, which are forbidden inside
++ * vm->mutex, get the first rpm wakeref outside of the mutex.
++ */
++ wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm);
+
+ if (flags & vma->vm->bind_async_flags) {
+ /* lock VM */
+@@ -1560,8 +1589,7 @@ err_fence:
+ if (work)
+ dma_fence_work_commit_imm(&work->base);
+ err_rpm:
+- if (wakeref)
+- intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref);
++ intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref);
+
+ if (moving)
+ dma_fence_put(moving);
projects / thirdparty / kernel / stable-queue.git / commitdiff
