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Subject[PATCH] rtc: nvmem: fix possible use after free
Date
In cas of probe failure, devres may free the memory allocated for
rtc->nvram before devm_rtc_release_device() is called. This leads to
rtc_nvram_unregister using it after being freed which may lead to a crash.

This has been shown to happen after commit 461e557b9727 ("rtc: nvmem: use
devm_nvmem_register()")

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
drivers/rtc/nvmem.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/rtc/nvmem.c b/drivers/rtc/nvmem.c
index ebdfe8e3a1a0..dce518d5e50e 100644
--- a/drivers/rtc/nvmem.c
+++ b/drivers/rtc/nvmem.c
@@ -12,6 +12,7 @@
#include <linux/types.h>
#include <linux/nvmem-consumer.h>
#include <linux/rtc.h>
+#include <linux/slab.h>
#include <linux/sysfs.h>

/*
@@ -45,9 +46,7 @@ static int rtc_nvram_register(struct rtc_device *rtc,
{
int err;

- rtc->nvram = devm_kzalloc(rtc->dev.parent,
- sizeof(struct bin_attribute),
- GFP_KERNEL);
+ rtc->nvram = kzalloc(sizeof(struct bin_attribute), GFP_KERNEL);
if (!rtc->nvram)
return -ENOMEM;

@@ -64,7 +63,7 @@ static int rtc_nvram_register(struct rtc_device *rtc,
err = sysfs_create_bin_file(&rtc->dev.parent->kobj,
rtc->nvram);
if (err) {
- devm_kfree(rtc->dev.parent, rtc->nvram);
+ kfree(rtc->nvram);
rtc->nvram = NULL;
}

@@ -74,6 +73,8 @@ static int rtc_nvram_register(struct rtc_device *rtc,
static void rtc_nvram_unregister(struct rtc_device *rtc)
{
sysfs_remove_bin_file(&rtc->dev.parent->kobj, rtc->nvram);
+ kfree(rtc->nvram);
+ rtc->nvram = NULL;
}

/*
--
2.20.1
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