Commit 2a0b390b authored Dec 19, 2019 by Jia-Ju Bai Committed by Miquel Raynal Jan 27, 2020

mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp()



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, the spinlock is replaced with a mutex.

These bugs are found by a static analysis tool STCheck written by
myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

parent e42617b8

drivers/mtd/maps/pcmciamtd.c

+3 −4

Original line number	Diff line number	Diff line
		@@ -294,16 +294,15 @@ static void pcmcia_copy_to(struct map_info map, unsigned long to, const void f
		}


		static DEFINE_SPINLOCK(pcmcia_vpp_lock);
		static DEFINE_MUTEX(pcmcia_vpp_lock);
		static int pcmcia_vpp_refcnt;
		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;

		pr_debug("dev = %p on = %d vpp = %d\n\n", dev, on, dev->vpp);
		spin_lock_irqsave(&pcmcia_vpp_lock, flags);
		mutex_lock(&pcmcia_vpp_lock);
		if (on) {
		if (++pcmcia_vpp_refcnt == 1) /* first nested 'on' */
		pcmcia_fixup_vpp(link, dev->vpp);
		@@ -311,7 +310,7 @@ static void pcmciamtd_set_vpp(struct map_info *map, int on)
		if (--pcmcia_vpp_refcnt == 0) /* last nested 'off' */
		pcmcia_fixup_vpp(link, 0);
		}
		spin_unlock_irqrestore(&pcmcia_vpp_lock, flags);
		mutex_unlock(&pcmcia_vpp_lock);
		}

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