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Subject[PATCH] spi: Make master->handle_err() callback optional to avoid crashes
Date
If a driver doesn't implement the master->handle_err() callback and an
SPI transfer fails, the kernel will crash with a NULL pointer
dereference:

Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0003000
[00000000] *pgd=80000040004003, *pmd=00000000
Internal error: Oops: 80000206 [#1] SMP ARM
Modules linked in:
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.0.0-rc7-koelsch-05861-g1fc9fdd4add4f783 #1046
Hardware name: Generic R8A7791 (Flattened Device Tree)
task: eec359c0 ti: eec54000 task.ti: eec54000
PC is at 0x0
LR is at spi_transfer_one_message+0x1cc/0x1f0

Make the master->handle_err() callback optional to avoid the crash.

Also fix a spelling mistake in the callback documentation while we're at
it.

Fixes: b716c4ffc6a2b0bf ("spi: introduce master->handle_err() callback")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
drivers/spi/spi.c | 2 +-
include/linux/spi/spi.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 04e9d9262711a56e..d5d7d2235163f9ef 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -736,7 +736,7 @@ out:
if (msg->status == -EINPROGRESS)
msg->status = ret;

- if (msg->status)
+ if (msg->status && master->handle_err)
master->handle_err(master, msg);

spi_finalize_current_message(master);
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 57a89347b038e611..d673072346f2e041 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -290,7 +290,7 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
* transfer_one_message are mutually exclusive; when both
* are set, the generic subsystem does not call your
* transfer_one callback.
- * @handle_err: the subsystem calls the driver to handle and error that occurs
+ * @handle_err: the subsystem calls the driver to handle an error that occurs
* in the generic implementation of transfer_one_message().
* @unprepare_message: undo any work done by prepare_message().
* @cs_gpios: Array of GPIOs to use as chip select lines; one per CS
--
1.9.1


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