[PATCH v3] drm/i915/vma: Fix UAF on reopen vs destroy race
Janusz Krzysztofik
janusz.krzysztofik at linux.intel.com
Mon Apr 15 19:53:09 UTC 2024
We defer actually closing, unbinding and destroying a VMA until next idle
point, or until the object is freed in the meantime. By postponing the
unbind, we allow for the VMA to be reopened by the client, avoiding the
work required to rebind the VMA.
It was assumed that as long as a GT is held idle, no VMA would be reopened
while we destroy them. That assumption is no longer true in multi-GT
configurations, where a VMA we reopen may be handled by a GT different
from the one that we already keep active via its engine while we set up
an execbuf request.
<4> [260.290809] ------------[ cut here ]------------
<4> [260.290988] list_del corruption. prev->next should be ffff888118c5d990, but was ffff888118c5a510. (prev=ffff888118c5a510)
<4> [260.291004] WARNING: CPU: 2 PID: 1143 at lib/list_debug.c:62 __list_del_entry_valid_or_report+0xb7/0xe0
..
<4> [260.291055] CPU: 2 PID: 1143 Comm: kms_plane Not tainted 6.9.0-rc2-CI_DRM_14524-ga25d180c6853+ #1
<4> [260.291058] Hardware name: Intel Corporation Meteor Lake Client Platform/MTL-P LP5x T3 RVP, BIOS MTLPFWI1.R00.3471.D91.2401310918 01/31/2024
<4> [260.291060] RIP: 0010:__list_del_entry_valid_or_report+0xb7/0xe0
...
<4> [260.291087] Call Trace:
<4> [260.291089] <TASK>
<4> [260.291124] i915_vma_reopen+0x43/0x80 [i915]
<4> [260.291298] eb_lookup_vmas+0x9cb/0xcc0 [i915]
<4> [260.291579] i915_gem_do_execbuffer+0xc9a/0x26d0 [i915]
<4> [260.291883] i915_gem_execbuffer2_ioctl+0x123/0x2a0 [i915]
...
<4> [260.292301] </TASK>
...
<4> [260.292506] ---[ end trace 0000000000000000 ]---
<4> [260.292782] general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6ca3: 0000 [#1] PREEMPT SMP NOPTI
<4> [260.303575] CPU: 2 PID: 1143 Comm: kms_plane Tainted: G W 6.9.0-rc2-CI_DRM_14524-ga25d180c6853+ #1
<4> [260.313851] Hardware name: Intel Corporation Meteor Lake Client Platform/MTL-P LP5x T3 RVP, BIOS MTLPFWI1.R00.3471.D91.2401310918 01/31/2024
<4> [260.326359] RIP: 0010:eb_validate_vmas+0x114/0xd80 [i915]
...
<4> [260.428756] Call Trace:
<4> [260.431192] <TASK>
<4> [639.283393] i915_gem_do_execbuffer+0xd05/0x26d0 [i915]
<4> [639.305245] i915_gem_execbuffer2_ioctl+0x123/0x2a0 [i915]
...
<4> [639.411134] </TASK>
...
<4> [639.449979] ---[ end trace 0000000000000000 ]---
As soon as we start unbinding and destroying a VMA, marked it as parked,
and also keep it marked as closed for the rest of its life. When a VMA
to be opened occurs closed, reopen it only if not yet parked.
v3: Fix misplaced brackets.
v2: Since we no longer re-init the VMA closed list link on VMA park so it
looks like still on a list, don't try to delete it from the list again
after the VMA has been marked as parked.
Fixes: b0647a5e79b1 ("drm/i915: Avoid live-lock with i915_vma_parked()")
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10608
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
Cc: Chris Wilson <chris.p.wilson at linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: stable at vger.kernel.org # v6.0+
---
.../gpu/drm/i915/gem/i915_gem_execbuffer.c | 10 ++++--
drivers/gpu/drm/i915/i915_vma.c | 32 +++++++++++++++----
drivers/gpu/drm/i915/i915_vma.h | 2 +-
drivers/gpu/drm/i915/i915_vma_types.h | 3 ++
4 files changed, 37 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 42619fc05de48..97e014f94002e 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -847,9 +847,12 @@ static int __eb_add_lut(struct i915_execbuffer *eb,
if (unlikely(!lut))
return -ENOMEM;
+ if (!i915_vma_open(vma)) {
+ err = -EEXIST; /* let eb_vma_lookup() retry */
+ goto err_lut_free;
+ }
+
i915_vma_get(vma);
- if (!atomic_fetch_inc(&vma->open_count))
- i915_vma_reopen(vma);
lut->handle = handle;
lut->ctx = ctx;
@@ -880,8 +883,9 @@ static int __eb_add_lut(struct i915_execbuffer *eb,
return 0;
err:
- i915_vma_close(vma);
i915_vma_put(vma);
+ i915_vma_close(vma);
+err_lut_free:
i915_lut_handle_free(lut);
return err;
}
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index d2f064d2525cc..4435c76f28c8c 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -1735,14 +1735,33 @@ static void __i915_vma_remove_closed(struct i915_vma *vma)
list_del_init(&vma->closed_link);
}
-void i915_vma_reopen(struct i915_vma *vma)
+static struct i915_vma *i915_vma_reopen(struct i915_vma *vma)
+{
+ if (atomic_read(&vma->flags) & I915_VMA_PARKED)
+ return NULL;
+
+ __i915_vma_remove_closed(vma);
+ return vma;
+}
+
+struct i915_vma *i915_vma_open(struct i915_vma *vma)
{
struct intel_gt *gt = vma->vm->gt;
+ if (atomic_inc_not_zero(&vma->open_count))
+ return vma;
+
spin_lock_irq(>->closed_lock);
- if (i915_vma_is_closed(vma))
- __i915_vma_remove_closed(vma);
+ if (!atomic_inc_not_zero(&vma->open_count)) {
+ if (i915_vma_is_closed(vma))
+ vma = i915_vma_reopen(vma);
+
+ if (vma)
+ atomic_inc(&vma->open_count);
+ }
spin_unlock_irq(>->closed_lock);
+
+ return vma;
}
static void force_unbind(struct i915_vma *vma)
@@ -1770,7 +1789,8 @@ static void release_references(struct i915_vma *vma, struct intel_gt *gt,
spin_unlock(&obj->vma.lock);
spin_lock_irq(>->closed_lock);
- __i915_vma_remove_closed(vma);
+ if (!(atomic_read(&vma->flags) & I915_VMA_PARKED))
+ __i915_vma_remove_closed(vma);
spin_unlock_irq(>->closed_lock);
if (vm_ddestroy)
@@ -1854,22 +1874,22 @@ void i915_vma_parked(struct intel_gt *gt)
}
list_move(&vma->closed_link, &closed);
+ atomic_or(I915_VMA_PARKED, &vma->flags);
}
spin_unlock_irq(>->closed_lock);
- /* As the GT is held idle, no vma can be reopened as we destroy them */
list_for_each_entry_safe(vma, next, &closed, closed_link) {
struct drm_i915_gem_object *obj = vma->obj;
struct i915_address_space *vm = vma->vm;
if (i915_gem_object_trylock(obj, NULL)) {
- INIT_LIST_HEAD(&vma->closed_link);
i915_vma_destroy(vma);
i915_gem_object_unlock(obj);
} else {
/* back you go.. */
spin_lock_irq(>->closed_lock);
list_add(&vma->closed_link, >->closed_vma);
+ atomic_andnot(I915_VMA_PARKED, &vma->flags);
spin_unlock_irq(>->closed_lock);
}
diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
index e356dfb883d34..331d19672c764 100644
--- a/drivers/gpu/drm/i915/i915_vma.h
+++ b/drivers/gpu/drm/i915/i915_vma.h
@@ -268,7 +268,7 @@ int __must_check i915_vma_unbind_async(struct i915_vma *vma, bool trylock_vm);
int __must_check i915_vma_unbind_unlocked(struct i915_vma *vma);
void i915_vma_unlink_ctx(struct i915_vma *vma);
void i915_vma_close(struct i915_vma *vma);
-void i915_vma_reopen(struct i915_vma *vma);
+struct i915_vma *i915_vma_open(struct i915_vma *vma);
void i915_vma_destroy_locked(struct i915_vma *vma);
void i915_vma_destroy(struct i915_vma *vma);
diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h
index 559de74d0b114..41784c3025349 100644
--- a/drivers/gpu/drm/i915/i915_vma_types.h
+++ b/drivers/gpu/drm/i915/i915_vma_types.h
@@ -263,6 +263,9 @@ struct i915_vma {
#define I915_VMA_SCANOUT_BIT 17
#define I915_VMA_SCANOUT ((int)BIT(I915_VMA_SCANOUT_BIT))
+#define I915_VMA_PARKED_BIT 18
+#define I915_VMA_PARKED ((int)BIT(I915_VMA_PARKED_BIT))
+
struct i915_active active;
#define I915_VMA_PAGES_BIAS 24
--
2.44.0
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