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rtc: nvmem: fix possible use after free

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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 461e557b97 ("rtc: nvmem: use
devm_nvmem_register()")

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Alexandre Belloni 2018-12-31 00:49:36 +01:00
parent e01b578195
commit bba3d2daa8
1 changed files with 5 additions and 4 deletions
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9
drivers/rtc/nvmem.c
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@ -12,6 +12,7 @@
#include <linux/types.h> #include <linux/types.h>
#include <linux/nvmem-consumer.h> #include <linux/nvmem-consumer.h>
#include <linux/rtc.h> #include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/sysfs.h> #include <linux/sysfs.h>
/* /*
@ -45,9 +46,7 @@ static int rtc_nvram_register(struct rtc_device *rtc,
{ {
int err; int err;
rtc->nvram = devm_kzalloc(rtc->dev.parent, rtc->nvram = kzalloc(sizeof(struct bin_attribute), GFP_KERNEL);
sizeof(struct bin_attribute),
GFP_KERNEL);
if (!rtc->nvram) if (!rtc->nvram)
return -ENOMEM; return -ENOMEM;
@ -64,7 +63,7 @@ static int rtc_nvram_register(struct rtc_device *rtc,
err = sysfs_create_bin_file(&rtc->dev.parent->kobj, err = sysfs_create_bin_file(&rtc->dev.parent->kobj,
rtc->nvram); rtc->nvram);
if (err) { if (err) {
devm_kfree(rtc->dev.parent, rtc->nvram); kfree(rtc->nvram);
rtc->nvram = NULL; 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) static void rtc_nvram_unregister(struct rtc_device *rtc)
{ {
sysfs_remove_bin_file(&rtc->dev.parent->kobj, rtc->nvram); sysfs_remove_bin_file(&rtc->dev.parent->kobj, rtc->nvram);
kfree(rtc->nvram);
rtc->nvram = NULL;
} }
/* /*