From 001c8e83646ad3b847b18f6ac55a54367d917d74 Mon Sep 17 00:00:00 2001 From: "William A. Kennington III" Date: Wed, 7 Apr 2021 02:55:27 -0700 Subject: [PATCH] spi: Fix use-after-free with devm_spi_alloc_* [ Upstream commit 794aaf01444d4e765e2b067cba01cc69c1c68ed9 ] 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 [] (refcount_warn_saturate) from [] (kobject_put+0x90/0x98) [] (kobject_put) from [] (put_device+0x20/0x24) r4:b6700140 [] (put_device) from [] (devm_spi_release_controller+0x3c/0x40) [] (devm_spi_release_controller) from [] (release_nodes+0x84/0xc4) r5:b6700180 r4:b6700100 [] (release_nodes) from [] (devres_release_all+0x5c/0x60) r8:b1638c54 r7:b117ad94 r6:b1638c10 r5:b117ad94 r4:b163dc10 [] (devres_release_all) from [] (__device_release_driver+0x144/0x1ec) r5:b117ad94 r4:b163dc10 [] (__device_release_driver) from [] (device_driver_detach+0x84/0xa0) r9:00000000 r8:00000000 r7:b117ad94 r6:b163dc54 r5:b1638c10 r4:b163dc10 [] (device_driver_detach) from [] (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 Link: https://lore.kernel.org/r/20210407095527.2771582-1-wak@google.com Signed-off-by: Mark Brown Signed-off-by: Sasha Levin --- drivers/spi/spi.c | 9 ++------- include/linux/spi/spi.h | 3 +++ 2 files changed, 5 insertions(+), 7 deletions(-) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index e1205d72be52..7592d4de20c9 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -2291,6 +2291,7 @@ struct spi_controller *__devm_spi_alloc_controller(struct device *dev, ctlr = __spi_alloc_controller(dev, size, slave); if (ctlr) { + ctlr->devm_allocated = true; *ptr = ctlr; devres_add(dev, ptr); } else { @@ -2620,11 +2621,6 @@ int devm_spi_register_controller(struct device *dev, } EXPORT_SYMBOL_GPL(devm_spi_register_controller); -static int devm_spi_match_controller(struct device *dev, void *res, void *ctlr) -{ - return *(struct spi_controller **)res == ctlr; -} - static int __unregister(struct device *dev, void *null) { spi_unregister_device(to_spi_device(dev)); @@ -2671,8 +2667,7 @@ void spi_unregister_controller(struct spi_controller *ctlr) /* Release the last reference on the controller if its driver * has not yet been converted to devm_spi_alloc_master/slave(). */ - if (!devres_find(ctlr->dev.parent, devm_spi_release_controller, - devm_spi_match_controller, ctlr)) + if (!ctlr->devm_allocated) put_device(&ctlr->dev); /* free bus id */ diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index acd91300a4ab..7067f85cef0b 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -466,6 +466,9 @@ struct spi_controller { #define SPI_MASTER_GPIO_SS BIT(5) /* GPIO CS must select slave */ + /* flag indicating this is a non-devres managed controller */ + bool devm_allocated; + /* flag indicating this is an SPI slave controller */ bool slave;