linux-kernel - [PATCH 5.4 102/168] dmaengine: tegra-apb: Fix use-after-free

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Date:   Tue, 10 Mar 2020 13:39:08 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Osipenko <digetx@...il.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Vinod Koul <vkoul@...nel.org>
Subject: [PATCH 5.4 102/168] dmaengine: tegra-apb: Fix use-after-free

From: Dmitry Osipenko <digetx@...il.com>

commit 94788af4ed039476ff3527b0e6a12c1dc42cb022 upstream.

I was doing some experiments with I2C and noticed that Tegra APB DMA
driver crashes sometime after I2C DMA transfer termination. The crash
happens because tegra_dma_terminate_all() bails out immediately if pending
list is empty, and thus, it doesn't release the half-completed descriptors
which are getting re-used before ISR tasklet kicks-in.

 tegra-i2c 7000c400.i2c: DMA transfer timeout
 elants_i2c 0-0010: elants_i2c_irq: failed to read data: -110
 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 142 at lib/list_debug.c:45 __list_del_entry_valid+0x45/0xac
 list_del corruption, ddbaac44->next is LIST_POISON1 (00000100)
 Modules linked in:
 CPU: 0 PID: 142 Comm: kworker/0:2 Not tainted 5.5.0-rc2-next-20191220-00175-gc3605715758d-dirty #538
 Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
 Workqueue: events_freezable_power_ thermal_zone_device_check
 [<c010e5c5>] (unwind_backtrace) from [<c010a1c5>] (show_stack+0x11/0x14)
 [<c010a1c5>] (show_stack) from [<c0973925>] (dump_stack+0x85/0x94)
 [<c0973925>] (dump_stack) from [<c011f529>] (__warn+0xc1/0xc4)
 [<c011f529>] (__warn) from [<c011f7e9>] (warn_slowpath_fmt+0x61/0x78)
 [<c011f7e9>] (warn_slowpath_fmt) from [<c042497d>] (__list_del_entry_valid+0x45/0xac)
 [<c042497d>] (__list_del_entry_valid) from [<c047a87f>] (tegra_dma_tasklet+0x5b/0x154)
 [<c047a87f>] (tegra_dma_tasklet) from [<c0124799>] (tasklet_action_common.constprop.0+0x41/0x7c)
 [<c0124799>] (tasklet_action_common.constprop.0) from [<c01022ab>] (__do_softirq+0xd3/0x2a8)
 [<c01022ab>] (__do_softirq) from [<c0124683>] (irq_exit+0x7b/0x98)
 [<c0124683>] (irq_exit) from [<c0168c19>] (__handle_domain_irq+0x45/0x80)
 [<c0168c19>] (__handle_domain_irq) from [<c043e429>] (gic_handle_irq+0x45/0x7c)
 [<c043e429>] (gic_handle_irq) from [<c0101aa5>] (__irq_svc+0x65/0x94)
 Exception stack(0xde2ebb90 to 0xde2ebbd8)

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
Acked-by: Jon Hunter <jonathanh@...dia.com>
Cc: <stable@...r.kernel.org>
Link: https://lore.kernel.org/r/20200209163356.6439-2-digetx@gmail.com
Signed-off-by: Vinod Koul <vkoul@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/dma/tegra20-apb-dma.c |    4 ----
 1 file changed, 4 deletions(-)

--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -756,10 +756,6 @@ static int tegra_dma_terminate_all(struc
 	bool was_busy;
 
 	spin_lock_irqsave(&tdc->lock, flags);
-	if (list_empty(&tdc->pending_sg_req)) {
-		spin_unlock_irqrestore(&tdc->lock, flags);
-		return 0;
-	}
 
 	if (!tdc->busy)
 		goto skip_dma_stop;