| From 3c24ff2a94d02a09ee1904dac035350b1e5346f5 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 7 Apr 2021 02:55:27 -0700 |
| Subject: spi: Fix use-after-free with devm_spi_alloc_* |
| |
| From: William A. Kennington III <wak@google.com> |
| |
| [ 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 |
| [<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> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| 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 ca9970a63fdf..da71a53b0df7 100644 |
| --- a/drivers/spi/spi.c |
| +++ b/drivers/spi/spi.c |
| @@ -2076,6 +2076,7 @@ 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 { |
| @@ -2304,11 +2305,6 @@ 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)); |
| @@ -2353,8 +2349,7 @@ 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 715bd276a041..a8f6606dd498 100644 |
| --- a/include/linux/spi/spi.h |
| +++ b/include/linux/spi/spi.h |
| @@ -452,6 +452,9 @@ 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; |
| |
| -- |
| 2.30.2 |
| |