[PATCH v2] drm/xe: Fix an out-of-bounds shift when invalidating TLB

[Thomas Hellström]

Hi, Lucas,

On Wed, 2025-03-26 at 16:16 +0100, Thomas Hellström wrote:
> When the size of the range invalidated is larger than
> rounddown_pow_of_two(ULONG_MAX),
> The function macro roundup_pow_of_two(length) will hit an out-of-
> bounds
> shift [1].
> 
> Use a full TLB invalidation for such cases.
> v2:
> - Use a define for the range size limit over which we use a full
>   TLB invalidation. (Lucas)
> - Use a better calculation of the limit.

Does your R-B hold also for v2?

Thanks,
Thomas


> 
> [1]:
> [   39.202421] ------------[ cut here ]------------
> [   39.202657] UBSAN: shift-out-of-bounds in
> ./include/linux/log2.h:57:13
> [   39.202673] shift exponent 64 is too large for 64-bit type 'long
> unsigned int'
> [   39.202688] CPU: 8 UID: 0 PID: 3129 Comm: xe_exec_system_ Tainted:
> G     U             6.14.0+ #10
> [   39.202690] Tainted: [U]=USER
> [   39.202690] Hardware name: ASUS System Product Name/PRIME B560M-A
> AC, BIOS 2001 02/01/2023
> [   39.202691] Call Trace:
> [   39.202692]  <TASK>
> [   39.202695]  dump_stack_lvl+0x6e/0xa0
> [   39.202699]  ubsan_epilogue+0x5/0x30
> [   39.202701]  __ubsan_handle_shift_out_of_bounds.cold+0x61/0xe6
> [   39.202705]  xe_gt_tlb_invalidation_range.cold+0x1d/0x3a [xe]
> [   39.202800]  ? find_held_lock+0x2b/0x80
> [   39.202803]  ? mark_held_locks+0x40/0x70
> [   39.202806]  xe_svm_invalidate+0x459/0x700 [xe]
> [   39.202897]  drm_gpusvm_notifier_invalidate+0x4d/0x70 [drm_gpusvm]
> [   39.202900]  __mmu_notifier_release+0x1f5/0x270
> [   39.202905]  exit_mmap+0x40e/0x450
> [   39.202912]  __mmput+0x45/0x110
> [   39.202914]  exit_mm+0xc5/0x130
> [   39.202916]  do_exit+0x21c/0x500
> [   39.202918]  ? lockdep_hardirqs_on_prepare+0xdb/0x190
> [   39.202920]  do_group_exit+0x36/0xa0
> [   39.202922]  get_signal+0x8f8/0x900
> [   39.202926]  arch_do_signal_or_restart+0x35/0x100
> [   39.202930]  syscall_exit_to_user_mode+0x1fc/0x290
> [   39.202932]  do_syscall_64+0xa1/0x180
> [   39.202934]  ? do_user_addr_fault+0x59f/0x8a0
> [   39.202937]  ? lock_release+0xd2/0x2a0
> [   39.202939]  ? do_user_addr_fault+0x5a9/0x8a0
> [   39.202942]  ? trace_hardirqs_off+0x4b/0xc0
> [   39.202944]  ? clear_bhb_loop+0x25/0x80
> [   39.202946]  ? clear_bhb_loop+0x25/0x80
> [   39.202947]  ? clear_bhb_loop+0x25/0x80
> [   39.202950]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
> [   39.202952] RIP: 0033:0x7fa945e543e1
> [   39.202961] Code: Unable to access opcode bytes at 0x7fa945e543b7.
> [   39.202962] RSP: 002b:00007ffca8fb4170 EFLAGS: 00000293
> [   39.202963] RAX: 000000000000003d RBX: 0000000000000000 RCX:
> 00007fa945e543e3
> [   39.202964] RDX: 0000000000000000 RSI: 00007ffca8fb41ac RDI:
> 00000000ffffffff
> [   39.202964] RBP: 00007ffca8fb4190 R08: 0000000000000000 R09:
> 00007fa945f600a0
> [   39.202965] R10: 0000000000000000 R11: 0000000000000293 R12:
> 0000000000000000
> [   39.202966] R13: 00007fa9460dd310 R14: 00007ffca8fb41ac R15:
> 0000000000000000
> [   39.202970]  </TASK>
> [   39.202970] ---[ end trace ]---
> 
> Fixes: 332dd0116c82 ("drm/xe: Add range based TLB invalidations")
> Cc: Matthew Brost <matthew.brost at intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: <stable at vger.kernel.org> # v6.8+
> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> Reviewed-by: Lucas De Marchi <lucas.demarchi at intel.com> #v1
> ---
>  drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> index 03072e094991..084cbdeba8ea 100644
> --- a/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> +++ b/drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c
> @@ -322,6 +322,13 @@ int xe_gt_tlb_invalidation_ggtt(struct xe_gt
> *gt)
>  	return 0;
>  }
>  
> +/*
> + * Ensure that roundup_pow_of_two(length) doesn't overflow.
> + * Note that roundup_pow_of_two() operates on unsigned long,
> + * not on u64.
> + */
> +#define MAX_RANGE_TLB_INVALIDATION_LENGTH
> (rounddown_pow_of_two(ULONG_MAX))
> +
>  /**
>   * xe_gt_tlb_invalidation_range - Issue a TLB invalidation on this
> GT for an
>   * address range
> @@ -346,6 +353,7 @@ int xe_gt_tlb_invalidation_range(struct xe_gt
> *gt,
>  	struct xe_device *xe = gt_to_xe(gt);
>  #define MAX_TLB_INVALIDATION_LEN	7
>  	u32 action[MAX_TLB_INVALIDATION_LEN];
> +	u64 length = end - start;
>  	int len = 0;
>  
>  	xe_gt_assert(gt, fence);
> @@ -358,11 +366,11 @@ int xe_gt_tlb_invalidation_range(struct xe_gt
> *gt,
>  
>  	action[len++] = XE_GUC_ACTION_TLB_INVALIDATION;
>  	action[len++] = 0; /* seqno, replaced in
> send_tlb_invalidation */
> -	if (!xe->info.has_range_tlb_invalidation) {
> +	if (!xe->info.has_range_tlb_invalidation ||
> +	    length > MAX_RANGE_TLB_INVALIDATION_LENGTH) {
>  		action[len++] =
> MAKE_INVAL_OP(XE_GUC_TLB_INVAL_FULL);
>  	} else {
>  		u64 orig_start = start;
> -		u64 length = end - start;
>  		u64 align;
>  
>  		if (length < SZ_4K)