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spi: Fix use-after-free with devm_spi_alloc_*

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commit 794aaf01444d4e765e2b067cba01cc69c1c68ed9 upstream.

We can't rely on the contents of the devres list during
spi_unregister_controller(), as the list is already torn down at the
time we perform devres_find() for devm_spi_release_controller. This
causes devices registered with devm_spi_alloc_{master,slave}() to be
mistakenly identified as legacy, non-devm managed devices and have their
reference counters decremented below 0.

------------[ cut here ]------------
WARNING: CPU: 1 PID: 660 at lib/refcount.c:28 refcount_warn_saturate+0x108/0x174
[<b0396f04>] (refcount_warn_saturate) from [<b03c56a4>] (kobject_put+0x90/0x98)
[<b03c5614>] (kobject_put) from [<b0447b4c>] (put_device+0x20/0x24)
 r4:b6700140
[<b0447b2c>] (put_device) from [<b07515e8>] (devm_spi_release_controller+0x3c/0x40)
[<b07515ac>] (devm_spi_release_controller) from [<b045343c>] (release_nodes+0x84/0xc4)
 r5:b6700180 r4:b6700100
[<b04533b8>] (release_nodes) from [<b0454160>] (devres_release_all+0x5c/0x60)
 r8:b1638c54 r7:b117ad94 r6:b1638c10 r5:b117ad94 r4:b163dc10
[<b0454104>] (devres_release_all) from [<b044e41c>] (__device_release_driver+0x144/0x1ec)
 r5:b117ad94 r4:b163dc10
[<b044e2d8>] (__device_release_driver) from [<b044f70c>] (device_driver_detach+0x84/0xa0)
 r9:00000000 r8:00000000 r7:b117ad94 r6:b163dc54 r5:b1638c10 r4:b163dc10
[<b044f688>] (device_driver_detach) from [<b044d274>] (unbind_store+0xe4/0xf8)

Instead, determine the devm allocation state as a flag on the
controller which is guaranteed to be stable during cleanup.

Fixes: 5e844cc37a5c ("spi: Introduce device-managed SPI controller allocation")
Signed-off-by: William A. Kennington III <wak@google.com>
Link: https://lore.kernel.org/r/20210407095527.2771582-1-wak@google.com
Signed-off-by: Mark Brown <broonie@kernel.org>
[lukas: backport to v4.9.270]
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
William A. Kennington III 2021-04-07 02:55:27 -07:00 committed by Greg Kroah-Hartman
parent 22c840596a
commit 8bf96425c9
2 changed files with 5 additions and 7 deletions
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9
drivers/spi/spi.c
View File

@ -1869,6 +1869,7 @@ struct spi_master *devm_spi_alloc_master(struct device *dev, unsigned int size)
master = spi_alloc_master(dev, size);
if (master) {
master->devm_allocated = true;
*ptr = master;
devres_add(dev, ptr);
} else {
@ -2059,11 +2060,6 @@ int devm_spi_register_master(struct device *dev, struct spi_master *master)
}
EXPORT_SYMBOL_GPL(devm_spi_register_master);
static int devm_spi_match_master(struct device *dev, void *res, void *master)
{
return *(struct spi_master **)res == master;
}
static int __unregister(struct device *dev, void *null)
{
spi_unregister_device(to_spi_device(dev));
@ -2102,8 +2098,7 @@ void spi_unregister_master(struct spi_master *master)
/* Release the last reference on the master if its driver
* has not yet been converted to devm_spi_alloc_master().
*/
if (!devres_find(master->dev.parent, devm_spi_release_master,
devm_spi_match_master, master))
if (!master->devm_allocated)
put_device(&master->dev);
if (IS_ENABLED(CONFIG_SPI_DYNAMIC))

3
include/linux/spi/spi.h
View File

@ -443,6 +443,9 @@ struct spi_master {
#define SPI_MASTER_MUST_RX BIT(3) /* requires rx */
#define SPI_MASTER_MUST_TX BIT(4) /* requires tx */
/* flag indicating this is a non-devres managed controller */
bool devm_allocated;
/*
* on some hardware transfer / message size may be constrained
* the limit may depend on device transfer settings