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* [PATCH v2] drm/xe: Prevent BIT() overflow when handling invalid prefetch region
@ 2025-11-12 18:10 Shuicheng Lin
  2025-11-12 18:19 ` ✓ CI.KUnit: success for drm/xe: Prevent BIT() overflow when handling invalid prefetch region (rev2) Patchwork
                   ` (3 more replies)
  0 siblings, 4 replies; 5+ messages in thread
From: Shuicheng Lin @ 2025-11-12 18:10 UTC (permalink / raw)
  To: intel-xe; +Cc: Shuicheng Lin, stable, Matthew Auld

If user provides a large value (such as 0x80) for parameter
prefetch_mem_region_instance in vm_bind ioctl, it will cause
BIT(prefetch_region) overflow as below:
"
 ------------[ cut here ]------------
 UBSAN: shift-out-of-bounds in drivers/gpu/drm/xe/xe_vm.c:3414:7
 shift exponent 128 is too large for 64-bit type 'long unsigned int'
 CPU: 8 UID: 0 PID: 53120 Comm: xe_exec_system_ Tainted: G        W           6.18.0-rc1-lgci-xe-kernel+ #200 PREEMPT(voluntary)
 Tainted: [W]=WARN
 Hardware name: ASUS System Product Name/PRIME Z790-P WIFI, BIOS 0812 02/24/2023
 Call Trace:
  <TASK>
  dump_stack_lvl+0xa0/0xc0
  dump_stack+0x10/0x20
  ubsan_epilogue+0x9/0x40
  __ubsan_handle_shift_out_of_bounds+0x10e/0x170
  ? mutex_unlock+0x12/0x20
  xe_vm_bind_ioctl.cold+0x20/0x3c [xe]
 ...
"
Fix it by validating prefetch_region before the BIT() usage.

v2: Add Closes and Cc stable kernels. (Matt)

Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6478
Cc: <stable@vger.kernel.org> # v6.8+
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>
---
 drivers/gpu/drm/xe/xe_vm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 8fb5cc6a69ec..7cac646bdf1c 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -3411,8 +3411,10 @@ static int vm_bind_ioctl_check_args(struct xe_device *xe, struct xe_vm *vm,
 				 op == DRM_XE_VM_BIND_OP_PREFETCH) ||
 		    XE_IOCTL_DBG(xe, prefetch_region &&
 				 op != DRM_XE_VM_BIND_OP_PREFETCH) ||
-		    XE_IOCTL_DBG(xe,  (prefetch_region != DRM_XE_CONSULT_MEM_ADVISE_PREF_LOC &&
-				       !(BIT(prefetch_region) & xe->info.mem_region_mask))) ||
+		    XE_IOCTL_DBG(xe, (prefetch_region != DRM_XE_CONSULT_MEM_ADVISE_PREF_LOC &&
+				      /* Guard against undefined shift in BIT(prefetch_region) */
+				      (prefetch_region >= (sizeof(xe->info.mem_region_mask) * 8) ||
+				      !(BIT(prefetch_region) & xe->info.mem_region_mask)))) ||
 		    XE_IOCTL_DBG(xe, obj &&
 				 op == DRM_XE_VM_BIND_OP_UNMAP) ||
 		    XE_IOCTL_DBG(xe, (flags & DRM_XE_VM_BIND_FLAG_MADVISE_AUTORESET) &&
-- 
2.49.0


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2025-11-12 18:10 [PATCH v2] drm/xe: Prevent BIT() overflow when handling invalid prefetch region Shuicheng Lin
2025-11-12 18:19 ` ✓ CI.KUnit: success for drm/xe: Prevent BIT() overflow when handling invalid prefetch region (rev2) Patchwork
2025-11-12 19:01 ` ✓ Xe.CI.BAT: " Patchwork
2025-11-13  0:48 ` ✓ Xe.CI.Full: " Patchwork
2025-11-14 14:05 ` [PATCH v2] drm/xe: Prevent BIT() overflow when handling invalid prefetch region Matthew Auld

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