2023-09-23 21:57:28

by Michał Mirosław

[permalink] [raw]
Subject: [PATCH 1/3] usb: chipidea: Fix DMA overwrite for Tegra

Tegra USB controllers seem to issue DMA in doubleword-sized chunks and thus
may write past the buffer provided. This is detected by SLUB:

=============================================================================
BUG kmalloc-64 (Tainted: G B ): kmalloc Redzone overwritten
-----------------------------------------------------------------------------

0x8555cd02-0x8555cd03 @offset=3330. First byte 0x0 instead of 0xcc
Allocated in usb_get_status+0x2b/0xac age=1 cpu=3 pid=41
__kmem_cache_alloc_node+0x12f/0x1e4
__kmalloc+0x33/0x8c
usb_get_status+0x2b/0xac
hub_probe+0x5e9/0xcec
usb_probe_interface+0xbf/0x21c
really_probe+0xa5/0x2c4
__driver_probe_device+0x75/0x174
driver_probe_device+0x31/0x94
__device_attach_driver+0x65/0xc0
bus_for_each_drv+0x4b/0x74
__device_attach+0x69/0x120
bus_probe_device+0x65/0x6c
device_add+0x48b/0x5f8
usb_set_configuration+0x37b/0x6b4
usb_generic_driver_probe+0x37/0x68
usb_probe_device+0x35/0xb4
Slab 0xbf622b80 objects=21 used=18 fp=0x8555cdc0 flags=0x800(slab|zone=0)
Object 0x8555cd00 @offset=3328 fp=0x00000000

Redzone 8555ccc0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
Redzone 8555ccd0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
Redzone 8555cce0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
Redzone 8555ccf0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
Object 8555cd00: 01 00 00 00 cc cc cc cc cc cc cc cc cc cc cc cc ................
Object 8555cd10: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
Object 8555cd20: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
Object 8555cd30: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
Redzone 8555cd40: cc cc cc cc ....
Padding 8555cd74: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZ
CPU: 3 PID: 41 Comm: kworker/3:1 Tainted: G B 6.6.0-rc1mq-00118-g59786f827ea1 #1115
Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
Workqueue: usb_hub_wq hub_event
[<8010ca28>] (unwind_backtrace) from [<801090a5>] (show_stack+0x11/0x14)
[<801090a5>] (show_stack) from [<805da2fb>] (dump_stack_lvl+0x4d/0x7c)
[<805da2fb>] (dump_stack_lvl) from [<8026464f>] (check_bytes_and_report+0xb3/0xe4)
[<8026464f>] (check_bytes_and_report) from [<802648e1>] (check_object+0x261/0x290)
[<802648e1>] (check_object) from [<802671b1>] (free_to_partial_list+0x105/0x3f8)
[<802671b1>] (free_to_partial_list) from [<80268613>] (__kmem_cache_free+0x103/0x128)
[<80268613>] (__kmem_cache_free) from [<80425a67>] (usb_get_status+0x73/0xac)
[<80425a67>] (usb_get_status) from [<80421b31>] (hub_probe+0x5e9/0xcec)
[<80421b31>] (hub_probe) from [<80428bbb>] (usb_probe_interface+0xbf/0x21c)
[<80428bbb>] (usb_probe_interface) from [<803ee13d>] (really_probe+0xa5/0x2c4)
[<803ee13d>] (really_probe) from [<803ee3d1>] (__driver_probe_device+0x75/0x174)
[<803ee3d1>] (__driver_probe_device) from [<803ee501>] (driver_probe_device+0x31/0x94)
usb 1-1: device descriptor read/8, error -71

Fixes: fc53d5279094 ("usb: chipidea: tegra: Support host mode")
Signed-off-by: Michał Mirosław <[email protected]>
---
drivers/usb/chipidea/host.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/chipidea/host.c b/drivers/usb/chipidea/host.c
index 08af26b762a2..abddd39d1ff1 100644
--- a/drivers/usb/chipidea/host.c
+++ b/drivers/usb/chipidea/host.c
@@ -411,12 +411,13 @@ static int ci_hdrc_alloc_dma_aligned_buffer(struct urb *urb, gfp_t mem_flags)
const unsigned int ci_hdrc_usb_dma_align = 32;
size_t kmalloc_size;

- if (urb->num_sgs || urb->sg || urb->transfer_buffer_length == 0 ||
- !((uintptr_t)urb->transfer_buffer & (ci_hdrc_usb_dma_align - 1)))
+ if (urb->num_sgs || urb->sg || urb->transfer_buffer_length == 0)
+ return 0;
+ if (!((uintptr_t)urb->transfer_buffer & (ci_hdrc_usb_dma_align - 1)) && !(urb->transfer_buffer_length & 3))
return 0;

/* Allocate a buffer with enough padding for alignment */
- kmalloc_size = urb->transfer_buffer_length +
+ kmalloc_size = ALIGN(urb->transfer_buffer_length, 4) +
sizeof(struct ci_hdrc_dma_aligned_buffer) +
ci_hdrc_usb_dma_align - 1;

--
2.39.2


2023-09-25 12:58:31

by Peter Chen

[permalink] [raw]
Subject: Re: [PATCH 1/3] usb: chipidea: Fix DMA overwrite for Tegra

On 23-09-23 21:41:55, Michał Mirosław wrote:
> Tegra USB controllers seem to issue DMA in doubleword-sized chunks and thus
> may write past the buffer provided. This is detected by SLUB:
>
> =============================================================================
> BUG kmalloc-64 (Tainted: G B ): kmalloc Redzone overwritten
> -----------------------------------------------------------------------------
>
> 0x8555cd02-0x8555cd03 @offset=3330. First byte 0x0 instead of 0xcc
> Allocated in usb_get_status+0x2b/0xac age=1 cpu=3 pid=41
> __kmem_cache_alloc_node+0x12f/0x1e4
> __kmalloc+0x33/0x8c
> usb_get_status+0x2b/0xac
> hub_probe+0x5e9/0xcec
> usb_probe_interface+0xbf/0x21c
> really_probe+0xa5/0x2c4
> __driver_probe_device+0x75/0x174
> driver_probe_device+0x31/0x94
> __device_attach_driver+0x65/0xc0
> bus_for_each_drv+0x4b/0x74
> __device_attach+0x69/0x120
> bus_probe_device+0x65/0x6c
> device_add+0x48b/0x5f8
> usb_set_configuration+0x37b/0x6b4
> usb_generic_driver_probe+0x37/0x68
> usb_probe_device+0x35/0xb4
> Slab 0xbf622b80 objects=21 used=18 fp=0x8555cdc0 flags=0x800(slab|zone=0)
> Object 0x8555cd00 @offset=3328 fp=0x00000000
>
> Redzone 8555ccc0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> Redzone 8555ccd0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> Redzone 8555cce0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> Redzone 8555ccf0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> Object 8555cd00: 01 00 00 00 cc cc cc cc cc cc cc cc cc cc cc cc ................
> Object 8555cd10: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> Object 8555cd20: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> Object 8555cd30: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> Redzone 8555cd40: cc cc cc cc ....
> Padding 8555cd74: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZ
> CPU: 3 PID: 41 Comm: kworker/3:1 Tainted: G B 6.6.0-rc1mq-00118-g59786f827ea1 #1115
> Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
> Workqueue: usb_hub_wq hub_event
> [<8010ca28>] (unwind_backtrace) from [<801090a5>] (show_stack+0x11/0x14)
> [<801090a5>] (show_stack) from [<805da2fb>] (dump_stack_lvl+0x4d/0x7c)
> [<805da2fb>] (dump_stack_lvl) from [<8026464f>] (check_bytes_and_report+0xb3/0xe4)
> [<8026464f>] (check_bytes_and_report) from [<802648e1>] (check_object+0x261/0x290)
> [<802648e1>] (check_object) from [<802671b1>] (free_to_partial_list+0x105/0x3f8)
> [<802671b1>] (free_to_partial_list) from [<80268613>] (__kmem_cache_free+0x103/0x128)
> [<80268613>] (__kmem_cache_free) from [<80425a67>] (usb_get_status+0x73/0xac)
> [<80425a67>] (usb_get_status) from [<80421b31>] (hub_probe+0x5e9/0xcec)
> [<80421b31>] (hub_probe) from [<80428bbb>] (usb_probe_interface+0xbf/0x21c)
> [<80428bbb>] (usb_probe_interface) from [<803ee13d>] (really_probe+0xa5/0x2c4)
> [<803ee13d>] (really_probe) from [<803ee3d1>] (__driver_probe_device+0x75/0x174)
> [<803ee3d1>] (__driver_probe_device) from [<803ee501>] (driver_probe_device+0x31/0x94)
> usb 1-1: device descriptor read/8, error -71
>
> Fixes: fc53d5279094 ("usb: chipidea: tegra: Support host mode")
> Signed-off-by: Michał Mirosław <[email protected]>
> ---
> drivers/usb/chipidea/host.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/chipidea/host.c b/drivers/usb/chipidea/host.c
> index 08af26b762a2..abddd39d1ff1 100644
> --- a/drivers/usb/chipidea/host.c
> +++ b/drivers/usb/chipidea/host.c
> @@ -411,12 +411,13 @@ static int ci_hdrc_alloc_dma_aligned_buffer(struct urb *urb, gfp_t mem_flags)
> const unsigned int ci_hdrc_usb_dma_align = 32;
> size_t kmalloc_size;
>
> - if (urb->num_sgs || urb->sg || urb->transfer_buffer_length == 0 ||
> - !((uintptr_t)urb->transfer_buffer & (ci_hdrc_usb_dma_align - 1)))
> + if (urb->num_sgs || urb->sg || urb->transfer_buffer_length == 0)
> + return 0;
> + if (!((uintptr_t)urb->transfer_buffer & (ci_hdrc_usb_dma_align - 1)) && !(urb->transfer_buffer_length & 3))
> return 0;
>
> /* Allocate a buffer with enough padding for alignment */
> - kmalloc_size = urb->transfer_buffer_length +
> + kmalloc_size = ALIGN(urb->transfer_buffer_length, 4) +
> sizeof(struct ci_hdrc_dma_aligned_buffer) +
> ci_hdrc_usb_dma_align - 1;
>

Would you please explain why you make these changes?

--

Thanks,
Peter Chen

2023-09-26 03:30:12

by Michał Mirosław

[permalink] [raw]
Subject: Re: [PATCH 1/3] usb: chipidea: Fix DMA overwrite for Tegra

On Mon, Sep 25, 2023 at 07:45:22PM +0800, Peter Chen wrote:
> On 23-09-23 21:41:55, Micha? Miros?aw wrote:
> > Tegra USB controllers seem to issue DMA in doubleword-sized chunks and thus
> > may write past the buffer provided. This is detected by SLUB:
> >
> > =============================================================================
> > BUG kmalloc-64 (Tainted: G B ): kmalloc Redzone overwritten
> > -----------------------------------------------------------------------------
> >
> > 0x8555cd02-0x8555cd03 @offset=3330. First byte 0x0 instead of 0xcc
> > Allocated in usb_get_status+0x2b/0xac age=1 cpu=3 pid=41
> > __kmem_cache_alloc_node+0x12f/0x1e4
> > __kmalloc+0x33/0x8c
> > usb_get_status+0x2b/0xac
> > hub_probe+0x5e9/0xcec
> > usb_probe_interface+0xbf/0x21c
> > really_probe+0xa5/0x2c4
> > __driver_probe_device+0x75/0x174
> > driver_probe_device+0x31/0x94
> > __device_attach_driver+0x65/0xc0
> > bus_for_each_drv+0x4b/0x74
> > __device_attach+0x69/0x120
> > bus_probe_device+0x65/0x6c
> > device_add+0x48b/0x5f8
> > usb_set_configuration+0x37b/0x6b4
> > usb_generic_driver_probe+0x37/0x68
> > usb_probe_device+0x35/0xb4
> > Slab 0xbf622b80 objects=21 used=18 fp=0x8555cdc0 flags=0x800(slab|zone=0)
> > Object 0x8555cd00 @offset=3328 fp=0x00000000
> >
> > Redzone 8555ccc0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > Redzone 8555ccd0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > Redzone 8555cce0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > Redzone 8555ccf0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > Object 8555cd00: 01 00 00 00 cc cc cc cc cc cc cc cc cc cc cc cc ................
> > Object 8555cd10: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > Object 8555cd20: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > Object 8555cd30: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > Redzone 8555cd40: cc cc cc cc ....
> > Padding 8555cd74: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZ
> > CPU: 3 PID: 41 Comm: kworker/3:1 Tainted: G B 6.6.0-rc1mq-00118-g59786f827ea1 #1115
> > Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
> > Workqueue: usb_hub_wq hub_event
> > [<8010ca28>] (unwind_backtrace) from [<801090a5>] (show_stack+0x11/0x14)
> > [<801090a5>] (show_stack) from [<805da2fb>] (dump_stack_lvl+0x4d/0x7c)
> > [<805da2fb>] (dump_stack_lvl) from [<8026464f>] (check_bytes_and_report+0xb3/0xe4)
> > [<8026464f>] (check_bytes_and_report) from [<802648e1>] (check_object+0x261/0x290)
> > [<802648e1>] (check_object) from [<802671b1>] (free_to_partial_list+0x105/0x3f8)
> > [<802671b1>] (free_to_partial_list) from [<80268613>] (__kmem_cache_free+0x103/0x128)
> > [<80268613>] (__kmem_cache_free) from [<80425a67>] (usb_get_status+0x73/0xac)
> > [<80425a67>] (usb_get_status) from [<80421b31>] (hub_probe+0x5e9/0xcec)
> > [<80421b31>] (hub_probe) from [<80428bbb>] (usb_probe_interface+0xbf/0x21c)
> > [<80428bbb>] (usb_probe_interface) from [<803ee13d>] (really_probe+0xa5/0x2c4)
> > [<803ee13d>] (really_probe) from [<803ee3d1>] (__driver_probe_device+0x75/0x174)
> > [<803ee3d1>] (__driver_probe_device) from [<803ee501>] (driver_probe_device+0x31/0x94)
> > usb 1-1: device descriptor read/8, error -71
> >
> > Fixes: fc53d5279094 ("usb: chipidea: tegra: Support host mode")
> > Signed-off-by: Micha? Miros?aw <[email protected]>
> > ---
> > drivers/usb/chipidea/host.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/usb/chipidea/host.c b/drivers/usb/chipidea/host.c
> > index 08af26b762a2..abddd39d1ff1 100644
> > --- a/drivers/usb/chipidea/host.c
> > +++ b/drivers/usb/chipidea/host.c
> > @@ -411,12 +411,13 @@ static int ci_hdrc_alloc_dma_aligned_buffer(struct urb *urb, gfp_t mem_flags)
> > const unsigned int ci_hdrc_usb_dma_align = 32;
> > size_t kmalloc_size;
> >
> > - if (urb->num_sgs || urb->sg || urb->transfer_buffer_length == 0 ||
> > - !((uintptr_t)urb->transfer_buffer & (ci_hdrc_usb_dma_align - 1)))
> > + if (urb->num_sgs || urb->sg || urb->transfer_buffer_length == 0)
> > + return 0;
> > + if (!((uintptr_t)urb->transfer_buffer & (ci_hdrc_usb_dma_align - 1)) && !(urb->transfer_buffer_length & 3))
> > return 0;
> >
> > /* Allocate a buffer with enough padding for alignment */
> > - kmalloc_size = urb->transfer_buffer_length +
> > + kmalloc_size = ALIGN(urb->transfer_buffer_length, 4) +
> > sizeof(struct ci_hdrc_dma_aligned_buffer) +
> > ci_hdrc_usb_dma_align - 1;
> >
>
> Would you please explain why you make these changes?

Can you point out what's unclear in the commit message? This is to fix
a buffer overflow by DMA from the USB controller as it seems to write
data 32-bit word at a time. What the patch does is extend the workaround
code to account for the extra room needed at the tail of the buffer.

Best Regards
Micha? Miros?aw

2023-09-26 12:14:10

by Peter Chen

[permalink] [raw]
Subject: Re: [PATCH 1/3] usb: chipidea: Fix DMA overwrite for Tegra

On 23-09-26 01:53:39, Michał Mirosław wrote:
> On Mon, Sep 25, 2023 at 07:45:22PM +0800, Peter Chen wrote:
> > On 23-09-23 21:41:55, Michał Mirosław wrote:
> > > Tegra USB controllers seem to issue DMA in doubleword-sized chunks and thus
> > > may write past the buffer provided. This is detected by SLUB:
> > >
> > > =============================================================================
> > > BUG kmalloc-64 (Tainted: G B ): kmalloc Redzone overwritten
> > > -----------------------------------------------------------------------------
> > >
> > > 0x8555cd02-0x8555cd03 @offset=3330. First byte 0x0 instead of 0xcc
> > > Allocated in usb_get_status+0x2b/0xac age=1 cpu=3 pid=41
> > > __kmem_cache_alloc_node+0x12f/0x1e4
> > > __kmalloc+0x33/0x8c
> > > usb_get_status+0x2b/0xac
> > > hub_probe+0x5e9/0xcec
> > > usb_probe_interface+0xbf/0x21c
> > > really_probe+0xa5/0x2c4
> > > __driver_probe_device+0x75/0x174
> > > driver_probe_device+0x31/0x94
> > > __device_attach_driver+0x65/0xc0
> > > bus_for_each_drv+0x4b/0x74
> > > __device_attach+0x69/0x120
> > > bus_probe_device+0x65/0x6c
> > > device_add+0x48b/0x5f8
> > > usb_set_configuration+0x37b/0x6b4
> > > usb_generic_driver_probe+0x37/0x68
> > > usb_probe_device+0x35/0xb4
> > > Slab 0xbf622b80 objects=21 used=18 fp=0x8555cdc0 flags=0x800(slab|zone=0)
> > > Object 0x8555cd00 @offset=3328 fp=0x00000000
> > >
> > > Redzone 8555ccc0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > > Redzone 8555ccd0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > > Redzone 8555cce0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > > Redzone 8555ccf0: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > > Object 8555cd00: 01 00 00 00 cc cc cc cc cc cc cc cc cc cc cc cc ................
> > > Object 8555cd10: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > > Object 8555cd20: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > > Object 8555cd30: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc ................
> > > Redzone 8555cd40: cc cc cc cc ....
> > > Padding 8555cd74: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZ
> > > CPU: 3 PID: 41 Comm: kworker/3:1 Tainted: G B 6.6.0-rc1mq-00118-g59786f827ea1 #1115
> > > Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
> > > Workqueue: usb_hub_wq hub_event
> > > [<8010ca28>] (unwind_backtrace) from [<801090a5>] (show_stack+0x11/0x14)
> > > [<801090a5>] (show_stack) from [<805da2fb>] (dump_stack_lvl+0x4d/0x7c)
> > > [<805da2fb>] (dump_stack_lvl) from [<8026464f>] (check_bytes_and_report+0xb3/0xe4)
> > > [<8026464f>] (check_bytes_and_report) from [<802648e1>] (check_object+0x261/0x290)
> > > [<802648e1>] (check_object) from [<802671b1>] (free_to_partial_list+0x105/0x3f8)
> > > [<802671b1>] (free_to_partial_list) from [<80268613>] (__kmem_cache_free+0x103/0x128)
> > > [<80268613>] (__kmem_cache_free) from [<80425a67>] (usb_get_status+0x73/0xac)
> > > [<80425a67>] (usb_get_status) from [<80421b31>] (hub_probe+0x5e9/0xcec)
> > > [<80421b31>] (hub_probe) from [<80428bbb>] (usb_probe_interface+0xbf/0x21c)
> > > [<80428bbb>] (usb_probe_interface) from [<803ee13d>] (really_probe+0xa5/0x2c4)
> > > [<803ee13d>] (really_probe) from [<803ee3d1>] (__driver_probe_device+0x75/0x174)
> > > [<803ee3d1>] (__driver_probe_device) from [<803ee501>] (driver_probe_device+0x31/0x94)
> > > usb 1-1: device descriptor read/8, error -71
> > >
> > > Fixes: fc53d5279094 ("usb: chipidea: tegra: Support host mode")
> > > Signed-off-by: Michał Mirosław <[email protected]>
> > > ---
> > > drivers/usb/chipidea/host.c | 7 ++++---
> > > 1 file changed, 4 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/usb/chipidea/host.c b/drivers/usb/chipidea/host.c
> > > index 08af26b762a2..abddd39d1ff1 100644
> > > --- a/drivers/usb/chipidea/host.c
> > > +++ b/drivers/usb/chipidea/host.c
> > > @@ -411,12 +411,13 @@ static int ci_hdrc_alloc_dma_aligned_buffer(struct urb *urb, gfp_t mem_flags)
> > > const unsigned int ci_hdrc_usb_dma_align = 32;
> > > size_t kmalloc_size;
> > >
> > > - if (urb->num_sgs || urb->sg || urb->transfer_buffer_length == 0 ||
> > > - !((uintptr_t)urb->transfer_buffer & (ci_hdrc_usb_dma_align - 1)))
> > > + if (urb->num_sgs || urb->sg || urb->transfer_buffer_length == 0)
> > > + return 0;
> > > + if (!((uintptr_t)urb->transfer_buffer & (ci_hdrc_usb_dma_align - 1)) && !(urb->transfer_buffer_length & 3))
> > > return 0;
> > >
> > > /* Allocate a buffer with enough padding for alignment */
> > > - kmalloc_size = urb->transfer_buffer_length +
> > > + kmalloc_size = ALIGN(urb->transfer_buffer_length, 4) +
> > > sizeof(struct ci_hdrc_dma_aligned_buffer) +
> > > ci_hdrc_usb_dma_align - 1;
> > >
> >
> > Would you please explain why you make these changes?
>
> Can you point out what's unclear in the commit message?

You may appended below words to commit log, current commit log looks too
simple.

> This is to fix
> a buffer overflow by DMA from the USB controller as it seems to write
> data 32-bit word at a time. What the patch does is extend the workaround
> code to account for the extra room needed at the tail of the buffer.
>
> Best Regards
> Michał Mirosław

--

Thanks,
Peter Chen