Commit ff61eb42 authored Apr 07, 2015 by Geert Uytterhoeven Committed by Mark Brown Apr 07, 2015

spi: Make master->handle_err() callback optional to avoid crashes



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: b716c4ff ("spi: introduce master->handle_err() callback")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>

parent b716c4ff

drivers/spi/spi.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -851,7 +851,7 @@ 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);

include/linux/spi/spi.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -294,7 +294,7 @@ 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

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