[PATCH 3.18 41/57] spi/pxa2xx: Clear cur_chip pointer before starting next message

Greg Kroah-Hartman
2015-02-03T23:47:05Z

From: Mika Westerberg <mika.westerberg@linux.intel.com>

commit c957e8f084e0d21febcd6b8a0ea9631eccc92f36 upstream.

Once the current message is finished, the driver notifies SPI core about
this by calling spi_finalize_current_message(). This function queues next
message to be transferred. If there are more messages in the queue, it is
possible that the driver is asked to transfer the next message at this
point.

When spi_finalize_current_message() returns the driver clears the
drv_data->cur_chip pointer to NULL. The problem is that if the driver
already started the next message clearing drv_data->cur_chip will cause
NULL pointer dereference which crashes the kernel like:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
IP: [<ffffffffa0022bc8>] cs_deassert+0x18/0x70 [spi_pxa2xx_platform]
PGD 78bb8067 PUD 37712067 PMD 0
Oops: 0000 [#1] SMP
Modules linked in:
CPU: 1 PID: 11 Comm: ksoftirqd/1 Tainted: G O 3.18.0-rc4-mjo #5
Hardware name: Intel Corp. VALLEYVIEW B3 PLATFORM/NOTEBOOK, BIOS MNW2CRB1.X64.0071.R30.1408131301 08/13/2014
task: ffff880077f9f290 ti: ffff88007a820000 task.ti: ffff88007a820000
RIP: 0010:[<ffffffffa0022bc8>] [<ffffffffa0022bc8>] cs_deassert+0x18/0x70 [spi_pxa2xx_platform]
RSP: 0018:ffff88007a823d08 EFLAGS: 00010202
RAX: 0000000000000008 RBX: ffff8800379a4430 RCX: 0000000000000026
RDX: 0000000000000000 RSI: 0000000000000246 RDI: ffff8800379a4430
RBP: ffff88007a823d18 R08: 00000000ffffffff R09: 000000007a9bc65a
R10: 000000000000028f R11: 0000000000000005 R12: ffff880070123e98
R13: ffff880070123de8 R14: 0000000000000100 R15: ffffc90004888000
FS: 0000000000000000(0000) GS:ffff880079a80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000048 CR3: 000000007029b000 CR4: 00000000001007e0
Stack:
ffff88007a823d58 ffff8800379a4430 ffff88007a823d48 ffffffffa0022c89
0000000000000000 ffff8800379a4430 0000000000000000 0000000000000006
ffff88007a823da8 ffffffffa0023be0 ffff88007a823dd8 ffffffff81076204
Call Trace:
[<ffffffffa0022c89>] giveback+0x69/0xa0 [spi_pxa2xx_platform]
[<ffffffffa0023be0>] pump_transfers+0x710/0x740 [spi_pxa2xx_platform]
[<ffffffff81076204>] ? pick_next_task_fair+0x744/0x830
[<ffffffff81049679>] tasklet_action+0xa9/0xe0
[<ffffffff81049a0e>] __do_softirq+0xee/0x280
[<ffffffff81049bc0>] run_ksoftirqd+0x20/0x40
[<ffffffff810646df>] smpboot_thread_fn+0xff/0x1b0
[<ffffffff810645e0>] ? SyS_setgroups+0x150/0x150
[<ffffffff81060f9d>] kthread+0xcd/0xf0
[<ffffffff81060ed0>] ? kthread_create_on_node+0x180/0x180
[<ffffffff8187a82c>] ret_from_fork+0x7c/0xb0

Fix this by clearing drv_data->cur_chip before we call spi_finalize_current_message().

Reported-by: Martin Oldfield <m@mjoldfield.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/spi/spi-pxa2xx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -402,8 +402,8 @@ static void giveback(struct driver_data
cs_deassert(drv_data);
}

- spi_finalize_current_message(drv_data->master);
drv_data->cur_chip = NULL;
+ spi_finalize_current_message(drv_data->master);
}

static void reset_sccr1(struct driver_data *drv_data)