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Subject[PATCH] mtd: maps: pcmciamtd: fix possible sleep-in-atomic-context bugs in pcmciamtd_set_vpp()
Date
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
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