Hi,
Static analysis on linux-next wit Coverity has found a potential null
pointer dereference in commit:
commit 70732504c53b2d3aae2cebc457515a304672d5bb
Author: Yongqiang Sun <yongqiang.sun@xxxxxxx>
Date: Fri Feb 19 14:50:23 2021 -0500
drm/amd/display: Implement dmub trace event
The analysis is as follows:
400 enum dmub_status dmub_srv_hw_init(struct dmub_srv *dmub,
401 const struct dmub_srv_hw_params
*params)
402 {
403 struct dmub_fb *inst_fb = params->fb[DMUB_WINDOW_0_INST_CONST];
404 struct dmub_fb *stack_fb = params->fb[DMUB_WINDOW_1_STACK];
405 struct dmub_fb *data_fb = params->fb[DMUB_WINDOW_2_BSS_DATA];
406 struct dmub_fb *bios_fb = params->fb[DMUB_WINDOW_3_VBIOS];
407 struct dmub_fb *mail_fb = params->fb[DMUB_WINDOW_4_MAILBOX];
408 struct dmub_fb *tracebuff_fb =
params->fb[DMUB_WINDOW_5_TRACEBUFF];
409 struct dmub_fb *fw_state_fb = params->fb[DMUB_WINDOW_6_FW_STATE];
410 struct dmub_fb *scratch_mem_fb =
params->fb[DMUB_WINDOW_7_SCRATCH_MEM];
411
412 struct dmub_rb_init_params rb_params, outbox0_rb_params;
413 struct dmub_window cw0, cw1, cw2, cw3, cw4, cw5, cw6;
414 struct dmub_region inbox1, outbox1, outbox0;
415
1. Condition !dmub->sw_init, taking false branch.
416 if (!dmub->sw_init)
417 return DMUB_STATUS_INVALID;
418
419 dmub->fb_base = params->fb_base;
420 dmub->fb_offset = params->fb_offset;
421 dmub->psp_version = params->psp_version;
422
2. Condition dmub->hw_funcs.reset, taking true branch.
423 if (dmub->hw_funcs.reset)
424 dmub->hw_funcs.reset(dmub);
425
3. Condition inst_fb, taking true branch.
4. Condition data_fb, taking true branch.
426 if (inst_fb && data_fb) {
427 cw0.offset.quad_part = inst_fb->gpu_addr;
428 cw0.region.base = DMUB_CW0_BASE;
429 cw0.region.top = cw0.region.base + inst_fb->size - 1;
430
431 cw1.offset.quad_part = stack_fb->gpu_addr;
432 cw1.region.base = DMUB_CW1_BASE;
433 cw1.region.top = cw1.region.base + stack_fb->size - 1;
434
5. Condition params->load_inst_const, taking true branch.
6. Condition dmub->hw_funcs.backdoor_load, taking true branch.
435 if (params->load_inst_const &&
dmub->hw_funcs.backdoor_load) {
436 /**
437 * Read back all the instruction memory so we
don't hang the
438 * DMCUB when backdoor loading if the write from
x86 hasn't been
439 * flushed yet. This only occurs in backdoor loading.
440 */
441 dmub_flush_buffer_mem(inst_fb);
442 dmub->hw_funcs.backdoor_load(dmub, &cw0, &cw1);
443 }
444
445 }
446
7. Condition inst_fb, taking true branch.
8. Condition data_fb, taking true branch.
9. Condition bios_fb, taking true branch.
10. Condition mail_fb, taking true branch.
11. Condition tracebuff_fb, taking false branch.
12. var_compare_op: Comparing tracebuff_fb to null implies that
tracebuff_fb might be null.
447 if (inst_fb && data_fb && bios_fb && mail_fb && tracebuff_fb &&
448 fw_state_fb && scratch_mem_fb) {
449 cw2.offset.quad_part = data_fb->gpu_addr;
450 cw2.region.base = DMUB_CW0_BASE + inst_fb->size;
451 cw2.region.top = cw2.region.base + data_fb->size;
452
453 cw3.offset.quad_part = bios_fb->gpu_addr;
454 cw3.region.base = DMUB_CW3_BASE;
455 cw3.region.top = cw3.region.base + bios_fb->size;
456
457 cw4.offset.quad_part = mail_fb->gpu_addr;
458 cw4.region.base = DMUB_CW4_BASE;
459 cw4.region.top = cw4.region.base + mail_fb->size;
460
461 /**
462 * Doubled the mailbox region to accomodate inbox and
outbox.
463 * Note: Currently, currently total mailbox size is
16KB. It is split
464 * equally into 8KB between inbox and outbox. If this
config is
465 * changed, then uncached base address configuration
of outbox1
466 * has to be updated in funcs->setup_out_mailbox.
467 */
468 inbox1.base = cw4.region.base;
469 inbox1.top = cw4.region.base + DMUB_RB_SIZE;
470 outbox1.base = inbox1.top;
471 outbox1.top = cw4.region.top;
472
473 cw5.offset.quad_part = tracebuff_fb->gpu_addr;
474 cw5.region.base = DMUB_CW5_BASE;
475 cw5.region.top = cw5.region.base + tracebuff_fb->size;
476
477 outbox0.base = DMUB_REGION5_BASE +
TRACE_BUFFER_ENTRY_OFFSET;
478 outbox0.top = outbox0.base + sizeof(struct
dmcub_trace_buf_entry) * PERF_TRACE_MAX_ENTRY;
479
480
481 cw6.offset.quad_part = fw_state_fb->gpu_addr;
482 cw6.region.base = DMUB_CW6_BASE;
483 cw6.region.top = cw6.region.base + fw_state_fb->size;
484
485 dmub->fw_state = fw_state_fb->cpu_addr;
486
487 dmub->scratch_mem_fb = *scratch_mem_fb;
488
489 if (dmub->hw_funcs.setup_windows)
490 dmub->hw_funcs.setup_windows(dmub, &cw2,
&cw3, &cw4,
491 &cw5, &cw6);
492
493 if (dmub->hw_funcs.setup_outbox0)
494 dmub->hw_funcs.setup_outbox0(dmub, &outbox0);
495
496 if (dmub->hw_funcs.setup_mailbox)
497 dmub->hw_funcs.setup_mailbox(dmub, &inbox1);
498 if (dmub->hw_funcs.setup_out_mailbox)
499 dmub->hw_funcs.setup_out_mailbox(dmub, &outbox1);
500 }
501
13. Condition mail_fb, taking true branch.
502 if (mail_fb) {
503 dmub_memset(&rb_params, 0, sizeof(rb_params));
504 rb_params.ctx = dmub;
505 rb_params.base_address = mail_fb->cpu_addr;
506 rb_params.capacity = DMUB_RB_SIZE;
507
508 dmub_rb_init(&dmub->inbox1_rb, &rb_params);
509
510 // Initialize outbox1 ring buffer
511 rb_params.ctx = dmub;
512 rb_params.base_address = (void *) ((uint64_t)
(mail_fb->cpu_addr) + DMUB_RB_SIZE);
513 rb_params.capacity = DMUB_RB_SIZE;
514 dmub_rb_init(&dmub->outbox1_rb, &rb_params);
515
516 }
517
518 dmub_memset(&outbox0_rb_params, 0, sizeof(outbox0_rb_params));
519 outbox0_rb_params.ctx = dmub;
Dereference after null check (FORWARD_NULL)
14. var_deref_op: Dereferencing null pointer tracebuff_fb.
520 outbox0_rb_params.base_address = (void
*)((uint64_t)(tracebuff_fb->cpu_addr) + TRACE_BUFFER_ENTRY_OFFSET);
521 outbox0_rb_params.capacity = sizeof(struct
dmcub_trace_buf_entry) * PERF_TRACE_MAX_ENTRY;
The check on line 447 implies that tracebuf_fb could possibly be null,
however on line 520 tracebuf_fb is being dereferenced, so there is a
possibly (perhaps unlikely) null pointer dereference issue here.
Colin
522 dmub_rb_init(&dmub->outbox0_rb, &outbox0_rb_params);
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