[RFC PATCH] drm/xe: fix memory leaks on vm_bind_ioctl failure paths

[Paulo Zanoni]

Caught by kmemleak when running Vulkan CTS tests on LNL. The leak
seems to happen only when there's some kind of failure happening, like
the lack of memory. Example output:

unreferenced object 0xffff9120bdf62000 (size 8192):
  comm "deqp-vk", pid 115008, jiffies 4310295728
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 1b 05 f9 28 01 00 00 40  ...........(...@
    00 00 00 00 00 00 00 00 1b 15 f9 28 01 00 00 40  ...........(...@
  backtrace (crc 7a56be79):
    [<ffffffff86dd81f0>] __kmalloc_cache_noprof+0x310/0x3d0
    [<ffffffffc08e8211>] xe_pt_new_shared.constprop.0+0x81/0xb0 [xe]
    [<ffffffffc08e8309>] xe_pt_insert_entry+0xb9/0x140 [xe]
    [<ffffffffc08eab6d>] xe_pt_stage_bind_entry+0x12d/0x5b0 [xe]
    [<ffffffffc08ecbca>] xe_pt_walk_range+0xea/0x280 [xe]
    [<ffffffffc08eccea>] xe_pt_walk_range+0x20a/0x280 [xe]
    [<ffffffffc08eccea>] xe_pt_walk_range+0x20a/0x280 [xe]
    [<ffffffffc08eccea>] xe_pt_walk_range+0x20a/0x280 [xe]
    [<ffffffffc08eccea>] xe_pt_walk_range+0x20a/0x280 [xe]
    [<ffffffffc08e9eff>] xe_pt_stage_bind.constprop.0+0x25f/0x580 [xe]
    [<ffffffffc08eb21a>] bind_op_prepare+0xea/0x6e0 [xe]
    [<ffffffffc08ebab8>] xe_pt_update_ops_prepare+0x1c8/0x440 [xe]
    [<ffffffffc08ffbf3>] ops_execute+0x143/0x850 [xe]
    [<ffffffffc0900b64>] vm_bind_ioctl_ops_execute+0x244/0x800 [xe]
    [<ffffffffc0906467>] xe_vm_bind_ioctl+0x1877/0x2370 [xe]
    [<ffffffffc05e92b3>] drm_ioctl_kernel+0xb3/0x110 [drm]
unreferenced object 0xffff9120bdf72000 (size 8192):
  comm "deqp-vk", pid 115008, jiffies 4310295728
  hex dump (first 32 bytes):
    6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
    6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
  backtrace (crc 23b2f0b5):
    [<ffffffff86dd81f0>] __kmalloc_cache_noprof+0x310/0x3d0
    [<ffffffffc08e8211>] xe_pt_new_shared.constprop.0+0x81/0xb0 [xe]
    [<ffffffffc08e8453>] xe_pt_stage_unbind_post_descend+0xb3/0x150 [xe]
    [<ffffffffc08ecd26>] xe_pt_walk_range+0x246/0x280 [xe]
    [<ffffffffc08eccea>] xe_pt_walk_range+0x20a/0x280 [xe]
    [<ffffffffc08eccea>] xe_pt_walk_range+0x20a/0x280 [xe]
    [<ffffffffc08eccea>] xe_pt_walk_range+0x20a/0x280 [xe]
    [<ffffffffc08ece31>] xe_pt_walk_shared+0xc1/0x110 [xe]
    [<ffffffffc08e7b2a>] xe_pt_stage_unbind+0x9a/0xd0 [xe]
    [<ffffffffc08e913d>] unbind_op_prepare+0xdd/0x270 [xe]
    [<ffffffffc08eb9f6>] xe_pt_update_ops_prepare+0x106/0x440 [xe]
    [<ffffffffc08ffbf3>] ops_execute+0x143/0x850 [xe]
    [<ffffffffc0900b64>] vm_bind_ioctl_ops_execute+0x244/0x800 [xe]
    [<ffffffffc0906467>] xe_vm_bind_ioctl+0x1877/0x2370 [xe]
    [<ffffffffc05e92b3>] drm_ioctl_kernel+0xb3/0x110 [drm]
    [<ffffffffc05e95a0>] drm_ioctl+0x280/0x4e0 [drm]

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/2877
Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/xe/xe_pt.c | 42 +++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 17 deletions(-)

PS: I'm not super confident that this is the right place to do this
since I'm not too familiar with this code and pointer ownership
changes a lot here. Still, this patch seems to work on my system, so
it may serve as a good conversation starter.

diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
index d6353e8969f0..212f7de645df 100644
--- a/drivers/gpu/drm/xe/xe_pt.c
+++ b/drivers/gpu/drm/xe/xe_pt.c
@@ -921,18 +921,23 @@ static void xe_pt_abort_bind(struct xe_vma *vma,
 		if (!rebind)
 			pt->num_live -= entries[i].qwords;
 
-		if (!pt->level)
-			continue;
-
-		pt_dir = as_xe_pt_dir(pt);
-		for (j = 0; j < entries[i].qwords; j++) {
-			u32 j_ = j + entries[i].ofs;
-			struct xe_pt *newpte = xe_pt_entry(pt_dir, j_);
-			struct xe_pt *oldpte = entries[i].pt_entries[j].pt;
-
-			pt_dir->children[j_] = oldpte ? &oldpte->base : 0;
-			xe_pt_destroy(newpte, xe_vma_vm(vma)->flags, NULL);
+		if (pt->level) {
+			pt_dir = as_xe_pt_dir(pt);
+			for (j = 0; j < entries[i].qwords; j++) {
+				u32 j_ = j + entries[i].ofs;
+				struct xe_pt *newpte = xe_pt_entry(pt_dir, j_);
+				struct xe_pt *oldpte =
+					entries[i].pt_entries[j].pt;
+
+				pt_dir->children[j_] = oldpte ?
+					&oldpte->base : 0;
+				xe_pt_destroy(newpte, xe_vma_vm(vma)->flags,
+					      NULL);
+			}
 		}
+
+		if (entries[i].pt_entries)
+			kfree(entries[i].pt_entries);
 	}
 }
 
@@ -1564,13 +1569,16 @@ static void xe_pt_abort_unbind(struct xe_vma *vma,
 
 		pt->num_live += entry->qwords;
 
-		if (!pt->level)
-			continue;
+		if (pt->level) {
+			for (j = entry->ofs; j < entry->ofs + entry->qwords; j++)
+				pt_dir->children[j] =
+					entries[i].pt_entries[j - entry->ofs].pt ?
+						&entries[i].pt_entries[j - entry->ofs].pt->base :
+						NULL;
+		}
 
-		for (j = entry->ofs; j < entry->ofs + entry->qwords; j++)
-			pt_dir->children[j] =
-				entries[i].pt_entries[j - entry->ofs].pt ?
-				&entries[i].pt_entries[j - entry->ofs].pt->base : NULL;
+		if (entry->pt_entries)
+			kfree(entry->pt_entries);
 	}
 }
 
-- 
2.45.2