* [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp()
@ 2019-12-18 14:05 Jia-Ju Bai
2019-12-18 17:28 ` Dominik Brodowski
0 siblings, 1 reply; 4+ messages in thread
From: Jia-Ju Bai @ 2019-12-18 14:05 UTC (permalink / raw)
To: miquel.raynal, richard, vigneshr; +Cc: linux-mtd, linux-kernel, Jia-Ju Bai
The driver may sleep while holding a spinlock.
The function call path (from bottom to top) in Linux 4.19 is:
drivers/pcmcia/pcmcia_resource.c, 312:
mutex_lock in pcmcia_fixup_vpp
drivers/mtd/maps/pcmciamtd.c, 309:
pcmcia_fixup_vpp in pcmciamtd_set_vpp
drivers/mtd/maps/pcmciamtd.c, 306:
_raw_spin_lock_irqsave in pcmciamtd_set_vpp
drivers/pcmcia/pcmcia_resource.c, 312:
mutex_lock in pcmcia_fixup_vpp
drivers/mtd/maps/pcmciamtd.c, 312:
pcmcia_fixup_vpp in pcmciamtd_set_vpp
drivers/mtd/maps/pcmciamtd.c, 306:
_raw_spin_lock_irqsave in pcmciamtd_set_vp
mutex_lock() may sleep at runtime.
To fix these bugs, pcmcia_fixup_vpp() is called without holding the
spinlock.
These bugs are found by a static analysis tool STCheck written by
myself.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
drivers/mtd/maps/pcmciamtd.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/mtd/maps/pcmciamtd.c b/drivers/mtd/maps/pcmciamtd.c
index 70bb403f69f7..d2cd1708aa49 100644
--- a/drivers/mtd/maps/pcmciamtd.c
+++ b/drivers/mtd/maps/pcmciamtd.c
@@ -301,17 +301,23 @@ static void pcmciamtd_set_vpp(struct map_info *map, int on)
struct pcmciamtd_dev *dev = (struct pcmciamtd_dev *)map->map_priv_1;
struct pcmcia_device *link = dev->p_dev;
unsigned long flags;
+ int fixup_flag = 0;
pr_debug("dev = %p on = %d vpp = %d\n\n", dev, on, dev->vpp);
spin_lock_irqsave(&pcmcia_vpp_lock, flags);
if (on) {
if (++pcmcia_vpp_refcnt == 1) /* first nested 'on' */
- pcmcia_fixup_vpp(link, dev->vpp);
+ fixup_flag = 1;
} else {
if (--pcmcia_vpp_refcnt == 0) /* last nested 'off' */
- pcmcia_fixup_vpp(link, 0);
+ fixup_flag = 2;
}
spin_unlock_irqrestore(&pcmcia_vpp_lock, flags);
+
+ if (fixup_flag == 1)
+ pcmcia_fixup_vpp(link, dev->vpp);
+ else if (fixup_flag == 2)
+ pcmcia_fixup_vpp(link, 0);
}
--
2.17.1
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp()
2019-12-18 14:05 [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp() Jia-Ju Bai
@ 2019-12-18 17:28 ` Dominik Brodowski
2019-12-19 2:32 ` Jia-Ju Bai
0 siblings, 1 reply; 4+ messages in thread
From: Dominik Brodowski @ 2019-12-18 17:28 UTC (permalink / raw)
To: Jia-Ju Bai; +Cc: miquel.raynal, richard, vigneshr, linux-mtd, linux-kernel
On Wed, Dec 18, 2019 at 10:05:52PM +0800, Jia-Ju Bai wrote:
> The driver may sleep while holding a spinlock.
> The function call path (from bottom to top) in Linux 4.19 is:
>
> drivers/pcmcia/pcmcia_resource.c, 312:
> mutex_lock in pcmcia_fixup_vpp
> drivers/mtd/maps/pcmciamtd.c, 309:
> pcmcia_fixup_vpp in pcmciamtd_set_vpp
> drivers/mtd/maps/pcmciamtd.c, 306:
> _raw_spin_lock_irqsave in pcmciamtd_set_vpp
>
> drivers/pcmcia/pcmcia_resource.c, 312:
> mutex_lock in pcmcia_fixup_vpp
> drivers/mtd/maps/pcmciamtd.c, 312:
> pcmcia_fixup_vpp in pcmciamtd_set_vpp
> drivers/mtd/maps/pcmciamtd.c, 306:
> _raw_spin_lock_irqsave in pcmciamtd_set_vp
>
> mutex_lock() may sleep at runtime.
Thanks for noticing this issue.
> To fix these bugs, pcmcia_fixup_vpp() is called without holding the
> spinlock.
I don't think that this is the right approach here -- we lose the protection
against races in calls to pcmcia_fixup_vpp(). Instead, we should change the
spinlock to a mutex, which seems to be sufficient here. Could you prepare
such a patch, please?
Thanks,
Dominik
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp()
2019-12-18 17:28 ` Dominik Brodowski
@ 2019-12-19 2:32 ` Jia-Ju Bai
0 siblings, 0 replies; 4+ messages in thread
From: Jia-Ju Bai @ 2019-12-19 2:32 UTC (permalink / raw)
To: Dominik Brodowski
Cc: miquel.raynal, richard, vigneshr, linux-mtd, linux-kernel
On 2019/12/19 1:28, Dominik Brodowski wrote:
> On Wed, Dec 18, 2019 at 10:05:52PM +0800, Jia-Ju Bai wrote:
>> The driver may sleep while holding a spinlock.
>> The function call path (from bottom to top) in Linux 4.19 is:
>>
>> drivers/pcmcia/pcmcia_resource.c, 312:
>> mutex_lock in pcmcia_fixup_vpp
>> drivers/mtd/maps/pcmciamtd.c, 309:
>> pcmcia_fixup_vpp in pcmciamtd_set_vpp
>> drivers/mtd/maps/pcmciamtd.c, 306:
>> _raw_spin_lock_irqsave in pcmciamtd_set_vpp
>>
>> drivers/pcmcia/pcmcia_resource.c, 312:
>> mutex_lock in pcmcia_fixup_vpp
>> drivers/mtd/maps/pcmciamtd.c, 312:
>> pcmcia_fixup_vpp in pcmciamtd_set_vpp
>> drivers/mtd/maps/pcmciamtd.c, 306:
>> _raw_spin_lock_irqsave in pcmciamtd_set_vp
>>
>> mutex_lock() may sleep at runtime.
> Thanks for noticing this issue.
>
>> To fix these bugs, pcmcia_fixup_vpp() is called without holding the
>> spinlock.
> I don't think that this is the right approach here -- we lose the protection
> against races in calls to pcmcia_fixup_vpp(). Instead, we should change the
> spinlock to a mutex, which seems to be sufficient here. Could you prepare
> such a patch, please?
Okay, thanks for the advice :)
I will send a new patch.
Best wishes,
Jia-Ju Bai
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp()
@ 2019-12-18 13:41 Jia-Ju Bai
0 siblings, 0 replies; 4+ messages in thread
From: Jia-Ju Bai @ 2019-12-18 13:41 UTC (permalink / raw)
To: miquel.raynal, richard, vigneshr; +Cc: linux-mtd, linux-kernel, Jia-Ju Bai
The driver may sleep while holding a spinlock.
The function call path (from bottom to top) in Linux 4.19 is:
drivers/pcmcia/pcmcia_resource.c, 312:
mutex_lock in pcmcia_fixup_vpp
drivers/mtd/maps/pcmciamtd.c, 309:
pcmcia_fixup_vpp in pcmciamtd_set_vpp
drivers/mtd/maps/pcmciamtd.c, 306:
_raw_spin_lock_irqsave in pcmciamtd_set_vpp
drivers/pcmcia/pcmcia_resource.c, 312:
mutex_lock in pcmcia_fixup_vpp
drivers/mtd/maps/pcmciamtd.c, 312:
pcmcia_fixup_vpp in pcmciamtd_set_vpp
drivers/mtd/maps/pcmciamtd.c, 306:
_raw_spin_lock_irqsave in pcmciamtd_set_vp
mutex_lock() may sleep at runtime.
To fix these bugs, pcmcia_fixup_vpp() is called without holding the
spinlock.
These bugs are found by a static analysis tool STCheck written by
myself.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
drivers/mtd/maps/pcmciamtd.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/mtd/maps/pcmciamtd.c b/drivers/mtd/maps/pcmciamtd.c
index 70bb403f69f7..d2cd1708aa49 100644
--- a/drivers/mtd/maps/pcmciamtd.c
+++ b/drivers/mtd/maps/pcmciamtd.c
@@ -301,17 +301,23 @@ static void pcmciamtd_set_vpp(struct map_info *map, int on)
struct pcmciamtd_dev *dev = (struct pcmciamtd_dev *)map->map_priv_1;
struct pcmcia_device *link = dev->p_dev;
unsigned long flags;
+ int fixup_flag = 0;
pr_debug("dev = %p on = %d vpp = %d\n\n", dev, on, dev->vpp);
spin_lock_irqsave(&pcmcia_vpp_lock, flags);
if (on) {
if (++pcmcia_vpp_refcnt == 1) /* first nested 'on' */
- pcmcia_fixup_vpp(link, dev->vpp);
+ fixup_flag = 1;
} else {
if (--pcmcia_vpp_refcnt == 0) /* last nested 'off' */
- pcmcia_fixup_vpp(link, 0);
+ fixup_flag = 2;
}
spin_unlock_irqrestore(&pcmcia_vpp_lock, flags);
+
+ if (fixup_flag == 1)
+ pcmcia_fixup_vpp(link, dev->vpp);
+ else if (fixup_flag == 2)
+ pcmcia_fixup_vpp(link, 0);
}
--
2.17.1
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-12-19 2:32 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2019-12-18 14:05 [PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp() Jia-Ju Bai
2019-12-18 17:28 ` Dominik Brodowski
2019-12-19 2:32 ` Jia-Ju Bai
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2019-12-18 13:41 Jia-Ju Bai
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