Re: Possible null pointer dereference in rcar-dmac.ko
Hi Laurent > I don't think this fully fixes the problem, as the rcar_dmac_isr_error() IRQ > handler is still registered before all this. Furthermore, at least some of > the > initialization at the end of rcar_dmac_chan_probe() has to be moved before > the > rcar_dmac_isr_channel() IRQ handler registration. > > Let's not commit a quick hack but fix the problem correctly, we should ensure > that all the initialization needed by IRQ handlers is performed before they > get registered. Yeah, indeed. We need v2 patch Best regards --- Kuninori Morimoto
Re: Possible null pointer dereference in rcar-dmac.ko
Hi Morimoto-san,
Thank you for the patch.
On Thursday 10 Aug 2017 02:09:21 Kuninori Morimoto wrote:
> Anton Volkov noticed that engine->dev is NULL before
> of_dma_controller_register() in probe.
> Thus there might be a NULL pointer dereference in
> rcar_dmac_chan_start_xfer while accessing chan->chan.device->dev which
> is equal to (&dmac->engine)->dev.
> To be more safety code, this patch initialize dmac->engine before it.
>
> Reported-by: Anton Volkov
> Signed-off-by: Kuninori Morimoto
> ---
>
> > Anton, Laurent
>
> I created this patch because noone posted it yesterday.
> Anton, you can use this patch and replace Author to you if you want.
> Thus, I used [RFC] on this patch
I don't think you have, the subject line is still "Re: Possible null pointer
dereference in rcar-dmac.ko" :-)
> drivers/dma/sh/rcar-dmac.c | 51 ---
> 1 file changed, 26 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index ffcadca..6d60628 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -1818,8 +1818,32 @@ static int rcar_dmac_probe(struct platform_device
> *pdev) goto error;
> }
>
> - /* Initialize the channels. */
> - INIT_LIST_HEAD(&dmac->engine.channels);
> + /* Initialize engine */
> + engine = &dmac->engine;
> +
> + dma_cap_set(DMA_MEMCPY, engine->cap_mask);
> + dma_cap_set(DMA_SLAVE, engine->cap_mask);
> +
> + engine->dev = &pdev->dev;
> + engine->copy_align = ilog2(RCAR_DMAC_MEMCPY_XFER_SIZE);
> +
> + engine->src_addr_widths = widths;
> + engine->dst_addr_widths = widths;
> + engine->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
> + engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
> +
> + engine->device_alloc_chan_resources =
rcar_dmac_alloc_chan_resources;
> + engine->device_free_chan_resources =
rcar_dmac_free_chan_resources;
> + engine->device_prep_dma_memcpy = rcar_dmac_prep_dma_memcpy;
> + engine->device_prep_slave_sg= rcar_dmac_prep_slave_sg;
> + engine->device_prep_dma_cyclic = rcar_dmac_prep_dma_cyclic;
> + engine->device_config = rcar_dmac_device_config;
> + engine->device_terminate_all=
rcar_dmac_chan_terminate_all;
> + engine->device_tx_status= rcar_dmac_tx_status;
> + engine->device_issue_pending= rcar_dmac_issue_pending;
> + engine->device_synchronize =
rcar_dmac_device_synchronize;
> +
> + INIT_LIST_HEAD(&engine->channels);
I don't think this fully fixes the problem, as the rcar_dmac_isr_error() IRQ
handler is still registered before all this. Furthermore, at least some of the
initialization at the end of rcar_dmac_chan_probe() has to be moved before the
rcar_dmac_isr_channel() IRQ handler registration.
Let's not commit a quick hack but fix the problem correctly, we should ensure
that all the initialization needed by IRQ handlers is performed before they
get registered.
> for (i = 0; i < dmac->n_channels; ++i) {
> ret = rcar_dmac_chan_probe(dmac, &dmac->channels[i],
> @@ -1839,29 +1863,6 @@ static int rcar_dmac_probe(struct platform_device
> *pdev) *
>* Default transfer size of 32 bytes requires 32-byte alignment.
>*/
> - engine = &dmac->engine;
> - dma_cap_set(DMA_MEMCPY, engine->cap_mask);
> - dma_cap_set(DMA_SLAVE, engine->cap_mask);
> -
> - engine->dev = &pdev->dev;
> - engine->copy_align = ilog2(RCAR_DMAC_MEMCPY_XFER_SIZE);
> -
> - engine->src_addr_widths = widths;
> - engine->dst_addr_widths = widths;
> - engine->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
> - engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
> -
> - engine->device_alloc_chan_resources = rcar_dmac_alloc_chan_resources;
> - engine->device_free_chan_resources = rcar_dmac_free_chan_resources;
> - engine->device_prep_dma_memcpy = rcar_dmac_prep_dma_memcpy;
> - engine->device_prep_slave_sg = rcar_dmac_prep_slave_sg;
> - engine->device_prep_dma_cyclic = rcar_dmac_prep_dma_cyclic;
> - engine->device_config = rcar_dmac_device_config;
> - engine->device_terminate_all = rcar_dmac_chan_terminate_all;
> - engine->device_tx_status = rcar_dmac_tx_status;
> - engine->device_issue_pending = rcar_dmac_issue_pending;
> - engine->device_synchronize = rcar_dmac_device_synchronize;
> -
> ret = dma_async_device_register(engine);
> if (ret < 0)
> goto error;
--
Regards,
Laurent Pinchart
Re: Possible null pointer dereference in rcar-dmac.ko
Anton Volkov noticed that engine->dev is NULL before
of_dma_controller_register() in probe.
Thus there might be a NULL pointer dereference in
rcar_dmac_chan_start_xfer while accessing chan->chan.device->dev which
is equal to (&dmac->engine)->dev.
To be more safety code, this patch initialize dmac->engine before it.
Reported-by: Anton Volkov
Signed-off-by: Kuninori Morimoto
---
> Anton, Laurent
I created this patch because noone posted it yesterday.
Anton, you can use this patch and replace Author to you if you want.
Thus, I used [RFC] on this patch
drivers/dma/sh/rcar-dmac.c | 51 +++---
1 file changed, 26 insertions(+), 25 deletions(-)
diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index ffcadca..6d60628 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1818,8 +1818,32 @@ static int rcar_dmac_probe(struct platform_device *pdev)
goto error;
}
- /* Initialize the channels. */
- INIT_LIST_HEAD(&dmac->engine.channels);
+ /* Initialize engine */
+ engine = &dmac->engine;
+
+ dma_cap_set(DMA_MEMCPY, engine->cap_mask);
+ dma_cap_set(DMA_SLAVE, engine->cap_mask);
+
+ engine->dev = &pdev->dev;
+ engine->copy_align = ilog2(RCAR_DMAC_MEMCPY_XFER_SIZE);
+
+ engine->src_addr_widths = widths;
+ engine->dst_addr_widths = widths;
+ engine->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
+ engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
+
+ engine->device_alloc_chan_resources =
rcar_dmac_alloc_chan_resources;
+ engine->device_free_chan_resources = rcar_dmac_free_chan_resources;
+ engine->device_prep_dma_memcpy = rcar_dmac_prep_dma_memcpy;
+ engine->device_prep_slave_sg= rcar_dmac_prep_slave_sg;
+ engine->device_prep_dma_cyclic = rcar_dmac_prep_dma_cyclic;
+ engine->device_config = rcar_dmac_device_config;
+ engine->device_terminate_all= rcar_dmac_chan_terminate_all;
+ engine->device_tx_status= rcar_dmac_tx_status;
+ engine->device_issue_pending= rcar_dmac_issue_pending;
+ engine->device_synchronize = rcar_dmac_device_synchronize;
+
+ INIT_LIST_HEAD(&engine->channels);
for (i = 0; i < dmac->n_channels; ++i) {
ret = rcar_dmac_chan_probe(dmac, &dmac->channels[i],
@@ -1839,29 +1863,6 @@ static int rcar_dmac_probe(struct platform_device *pdev)
*
* Default transfer size of 32 bytes requires 32-byte alignment.
*/
- engine = &dmac->engine;
- dma_cap_set(DMA_MEMCPY, engine->cap_mask);
- dma_cap_set(DMA_SLAVE, engine->cap_mask);
-
- engine->dev = &pdev->dev;
- engine->copy_align = ilog2(RCAR_DMAC_MEMCPY_XFER_SIZE);
-
- engine->src_addr_widths = widths;
- engine->dst_addr_widths = widths;
- engine->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
- engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
-
- engine->device_alloc_chan_resources = rcar_dmac_alloc_chan_resources;
- engine->device_free_chan_resources = rcar_dmac_free_chan_resources;
- engine->device_prep_dma_memcpy = rcar_dmac_prep_dma_memcpy;
- engine->device_prep_slave_sg = rcar_dmac_prep_slave_sg;
- engine->device_prep_dma_cyclic = rcar_dmac_prep_dma_cyclic;
- engine->device_config = rcar_dmac_device_config;
- engine->device_terminate_all = rcar_dmac_chan_terminate_all;
- engine->device_tx_status = rcar_dmac_tx_status;
- engine->device_issue_pending = rcar_dmac_issue_pending;
- engine->device_synchronize = rcar_dmac_device_synchronize;
-
ret = dma_async_device_register(engine);
if (ret < 0)
goto error;
--
1.9.1
Re: Possible null pointer dereference in rcar-dmac.ko
Hello, On Wednesday 09 Aug 2017 00:49:40 Kuninori Morimoto wrote: > Hi Anton > > # add Laurent > > > While searching for races in the Linux kernel I've come across > > "drivers/dma/sh/rcar-dmac.ko" module. Here is a question that I came > > up with while analyzing results. Lines are given using the info from > > Linux v4.12. > > > > Consider the following case: > > > > Thread 1:Thread 2: > > rcar_dmac_probe > > ->rcar_dmac_chan_probe > > > > (&dmac->channels[i]) > > > > rchan = &dmac->channels[i] > > chan = &rchan->chan > > devm_request_threaded_irq(rchan) > > chan->device = &dmac->enginercar_dmac_isr_channel > > > > ->rcar_dmac_isr_transfer_end(chan) > > > > ->rcar_dmac_chan_start_xfer(chan) > > > > engine->dev = &pdev->dev; chan.device->dev> > > (rcar-dmac.c: line 1828)(rcar-dmac.c: line 351) > > > > As far as I understand engine->dev is NULL before its initialization > > in probe. Thus there might be a NULL pointer dereference in > > rcar_dmac_chan_start_xfer while accessing chan->chan.device->dev which > > is equal to (&dmac->engine)->dev. Is this possible from your point of > > view? > > Very rare case, but not impossible (?). > I think these engine->xxx initialize should be done before > of_dma_controller_register(); > engine.channels is initialized independently somehow... There should be no interrupt pending at the time the interrupt handler is registered, but to be safe it's indeed a good practice to register the interrupt handler after everything else has been initialized. Patches are welcome :-) -- Regards, Laurent Pinchart
Re: Possible null pointer dereference in rcar-dmac.ko
Hi Anton # add Laurent > While searching for races in the Linux kernel I've come across > "drivers/dma/sh/rcar-dmac.ko" module. Here is a question that I came > up with while analyzing results. Lines are given using the info from > Linux v4.12. > > Consider the following case: > > Thread 1:Thread 2: > rcar_dmac_probe > ->rcar_dmac_chan_probe > (&dmac->channels[i]) > rchan = &dmac->channels[i] > chan = &rchan->chan > devm_request_threaded_irq(rchan) > chan->device = &dmac->enginercar_dmac_isr_channel > ->rcar_dmac_isr_transfer_end(chan) > ->rcar_dmac_chan_start_xfer(chan) > engine->dev = &pdev->dev; chan.device->dev> > (rcar-dmac.c: line 1828)(rcar-dmac.c: line 351) > > As far as I understand engine->dev is NULL before its initialization > in probe. Thus there might be a NULL pointer dereference in > rcar_dmac_chan_start_xfer while accessing chan->chan.device->dev which > is equal to (&dmac->engine)->dev. Is this possible from your point of > view? Very rare case, but not impossible (?). I think these engine->xxx initialize should be done before of_dma_controller_register(); engine.channels is initialized independently somehow... Best regards --- Kuninori Morimoto
Possible null pointer dereference in rcar-dmac.ko
Hello. While searching for races in the Linux kernel I've come across "drivers/dma/sh/rcar-dmac.ko" module. Here is a question that I came up with while analyzing results. Lines are given using the info from Linux v4.12. Consider the following case: Thread 1:Thread 2: rcar_dmac_probe ->rcar_dmac_chan_probe (&dmac->channels[i]) rchan = &dmac->channels[i] chan = &rchan->chan devm_request_threaded_irq(rchan) chan->device = &dmac->enginercar_dmac_isr_channel ->rcar_dmac_isr_transfer_end(chan) ->rcar_dmac_chan_start_xfer(chan) engine->dev = &pdev->dev; chan.device->dev> (rcar-dmac.c: line 1828)(rcar-dmac.c: line 351) As far as I understand engine->dev is NULL before its initialization in probe. Thus there might be a NULL pointer dereference in rcar_dmac_chan_start_xfer while accessing chan->chan.device->dev which is equal to (&dmac->engine)->dev. Is this possible from your point of view? Thank you for your time. -- Anton Volkov Linux Verification Center, ISPRAS web: http://linuxtesting.org e-mail: avol...@ispras.ru
