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tty/isicom: Fix a possible sleep-in-atomic bug in WaitTillCardIsFree 

The driver may sleep under a spinlock.
The function call paths are:
isicom_activate (acquire the spinlock)
  isicom_setup_board
    drop_dtr_rts
      WaitTillCardIsFree
        msleep --> may sleep

isicom_set_termios
  isicom_config_port
    drop_dtr
      WaitTillCardIsFree
        msleep --> may sleep

isicom_tiocmset
  drop_dtr
    WaitTillCardIsFree
      msleep --> may sleep

Though "in_atomic" is used to check atomic context,
but it is not recommended to use in driver code (see include/linux/preempt.h).

To fix it, only using mdelay instead.

This bug is found by my static analysis tool(DSAC) and checked by my code review.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jia-Ju Bai 2017-12-12 21:24:56 +08:00 committed by Greg Kroah-Hartman
parent be7e251d20
commit fe8e7acea2
1 changed files with 1 additions and 5 deletions
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6
drivers/tty/isicom.c
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@ -219,13 +219,9 @@ static struct isi_port isi_ports[PORT_COUNT];
static int WaitTillCardIsFree(unsigned long base)
{
unsigned int count = 0;
unsigned int a = in_atomic(); /* do we run under spinlock? */
while (!(inw(base + 0xe) & 0x1) && count++ < 100)
if (a)
mdelay(1);
else
msleep(1);
mdelay(1);
return !(inw(base + 0xe) & 0x1);
}