dmaengine: tegra-adma: Fix use-after-free

Summary

In the Linux kernel, the following vulnerability has been resolved: dmaengine: tegra-adma: Fix use-after-free A use-after-free bug exists in the Tegra ADMA driver when audio streams are terminated, particularly during XRUN conditions. The issue occurs when the DMA buffer is freed by tegra_adma_terminate_all() before the vchan completion tasklet finishes accessing it. The race condition follows this sequence: 1. DMA transfer completes, triggering an interrupt that schedules the completion tasklet (tasklet has not executed yet) 2. Audio playback stops, calling tegra_adma_terminate_all() which frees the DMA buffer memory via kfree() 3. The scheduled tasklet finally executes, calling vchan_complete() which attempts to access the already-freed memory Since tasklets can execute at any time after being scheduled, there is no guarantee that the buffer will remain valid when vchan_complete() runs. Fix this by properly synchronizing the virtual channel completion: - Calling vchan_terminate_vdesc() in tegra_adma_stop() to mark the descriptors as terminated instead of freeing the descriptor. - Add the callback tegra_adma_synchronize() that calls vchan_synchronize() which kills any pending tasklets and frees any terminated descriptors. Crash logs: [ 337.427523] BUG: KASAN: use-after-free in vchan_complete+0x124/0x3b0 [ 337.427544] Read of size 8 at addr ffff000132055428 by task swapper/0/0 [ 337.427562] Call trace: [ 337.427564] dump_backtrace+0x0/0x320 [ 337.427571] show_stack+0x20/0x30 [ 337.427575] dump_stack_lvl+0x68/0x84 [ 337.427584] print_address_description.constprop.0+0x74/0x2b8 [ 337.427590] kasan_report+0x1f4/0x210 [ 337.427598] __asan_load8+0xa0/0xd0 [ 337.427603] vchan_complete+0x124/0x3b0 [ 337.427609] tasklet_action_common.constprop.0+0x190/0x1d0 [ 337.427617] tasklet_action+0x30/0x40 [ 337.427623] __do_softirq+0x1a0/0x5c4 [ 337.427628] irq_exit+0x110/0x140 [ 337.427633] handle_domain_irq+0xa4/0xe0 [ 337.427640] gic_handle_irq+0x64/0x160 [ 337.427644] call_on_irq_stack+0x20/0x4c [ 337.427649] do_interrupt_handler+0x7c/0x90 [ 337.427654] el1_interrupt+0x30/0x80 [ 337.427659] el1h_64_irq_handler+0x18/0x30 [ 337.427663] el1h_64_irq+0x7c/0x80 [ 337.427667] cpuidle_enter_state+0xe4/0x540 [ 337.427674] cpuidle_enter+0x54/0x80 [ 337.427679] do_idle+0x2e0/0x380 [ 337.427685] cpu_startup_entry+0x2c/0x70 [ 337.427690] rest_init+0x114/0x130 [ 337.427695] arch_call_rest_init+0x18/0x24 [ 337.427702] start_kernel+0x380/0x3b4 [ 337.427706] __primary_switched+0xc0/0xc8