From: William A. Kennington III Date: Wed, 7 Apr 2021 09:55:27 +0000 (-0700) Subject: spi: Fix use-after-free with devm_spi_alloc_* X-Git-Tag: v4.4.271~37 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=62bb2c7f2411a0045c24831f11ecacfc35610815;p=thirdparty%2Fkernel%2Fstable.git spi: Fix use-after-free with devm_spi_alloc_* 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 [] (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 [lukas: backport to v4.4.270] Signed-off-by: Lukas Wunner Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index e85feee750e3d..f743b95d5171d 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1762,6 +1762,7 @@ 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 { @@ -1951,11 +1952,6 @@ 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)); @@ -1994,8 +1990,7 @@ 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)) diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index f5d387140c469..da487e9053371 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -425,6 +425,9 @@ 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; + /* lock and mutex for SPI bus locking */ spinlock_t bus_lock_spinlock; struct mutex bus_lock_mutex;