[PATCH v2 1/2] drm/xe: Fix vm_bind_ioctl double free bug

[Christoph Manszewski]

If the argument check during an array bind fails, the bind_ops are freed
twice as seen in [1]. Fix this by setting bind_ops to NULL after freeing.

[1]:
==================================================================
BUG: KASAN: double-free in xe_vm_bind_ioctl+0x1b2/0x21f0 [xe]
Free of addr ffff88813bb9b800 by task xe_vm/14198

CPU: 5 UID: 0 PID: 14198 Comm: xe_vm Not tainted 6.16.0-xe-eudebug-cmanszew+ #520 PREEMPT(full)
Hardware name: Intel Corporation Alder Lake Client Platform/AlderLake-P DDR5 RVP, BIOS ADLPFWI1.R00.2411.A02.2110081023 10/08/2021
Call Trace:
 <TASK>
 dump_stack_lvl+0x82/0xd0
 print_report+0xcb/0x610
 ? __virt_addr_valid+0x19a/0x300
 ? xe_vm_bind_ioctl+0x1b2/0x21f0 [xe]
 kasan_report_invalid_free+0xc8/0xf0
 ? xe_vm_bind_ioctl+0x1b2/0x21f0 [xe]
 ? xe_vm_bind_ioctl+0x1b2/0x21f0 [xe]
 check_slab_allocation+0x102/0x130
 kfree+0x10d/0x440
 ? should_fail_ex+0x57/0x2f0
 ? xe_vm_bind_ioctl+0x1b2/0x21f0 [xe]
 xe_vm_bind_ioctl+0x1b2/0x21f0 [xe]
 ? __pfx_xe_vm_bind_ioctl+0x10/0x10 [xe]
 ? __lock_acquire+0xab9/0x27f0
 ? lock_acquire+0x165/0x300
 ? drm_dev_enter+0x53/0xe0 [drm]
 ? find_held_lock+0x2b/0x80
 ? drm_dev_exit+0x30/0x50 [drm]
 ? drm_ioctl_kernel+0x128/0x1c0 [drm]
 drm_ioctl_kernel+0x128/0x1c0 [drm]
 ? __pfx_xe_vm_bind_ioctl+0x10/0x10 [xe]
 ? find_held_lock+0x2b/0x80
 ? __pfx_drm_ioctl_kernel+0x10/0x10 [drm]
 ? should_fail_ex+0x57/0x2f0
 ? __pfx_xe_vm_bind_ioctl+0x10/0x10 [xe]
 drm_ioctl+0x352/0x620 [drm]
 ? __pfx_drm_ioctl+0x10/0x10 [drm]
 ? __pfx_rpm_resume+0x10/0x10
 ? do_raw_spin_lock+0x11a/0x1b0
 ? find_held_lock+0x2b/0x80
 ? __pm_runtime_resume+0x61/0xc0
 ? rcu_is_watching+0x20/0x50
 ? trace_irq_enable.constprop.0+0xac/0xe0
 xe_drm_ioctl+0x91/0xc0 [xe]
 __x64_sys_ioctl+0xb2/0x100
 ? rcu_is_watching+0x20/0x50
 do_syscall_64+0x68/0x2e0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fa9acb24ded
Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1a 48 8b 45 c8 64 48 2b 04 25 28 00 00 00
RSP: 002b:00007fff189e1370 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: ffffffffffffff68 RCX: 00007fa9acb24ded
RDX: 00007fff189e19f0 RSI: 0000000040886445 RDI: 0000000000000003
RBP: 00007fff189e13c0 R08: 0000000000000000 R09: 00005561d3fb47d0
R10: 00007fa9ace29be0 R11: 0000000000000246 R12: 00007fff189e19f0
R13: 0000000040886445 R14: 0000000000000003 R15: 0000000000000003
 </TASK>

Fixes: b43e864af0d4 ("drm/xe/uapi: Add DRM_XE_VM_BIND_FLAG_CPU_ADDR_MIRROR")
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Signed-off-by: Christoph Manszewski <christoph.manszewski at intel.com>
---
 drivers/gpu/drm/xe/xe_vm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index d40d2d43c041..6fd28b205453 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -3442,6 +3442,7 @@ static int vm_bind_ioctl_check_args(struct xe_device *xe, struct xe_vm *vm,
 free_bind_ops:
 	if (args->num_binds > 1)
 		kvfree(*bind_ops);
+	*bind_ops = NULL;
 	return err;
 }
 
@@ -3548,7 +3549,7 @@ int xe_vm_bind_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 	struct xe_exec_queue *q = NULL;
 	u32 num_syncs, num_ufence = 0;
 	struct xe_sync_entry *syncs = NULL;
-	struct drm_xe_vm_bind_op *bind_ops;
+	struct drm_xe_vm_bind_op *bind_ops = NULL;
 	struct xe_vma_ops vops;
 	struct dma_fence *fence;
 	int err;
-- 
2.47.1