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Char: lp, protect LPGETSTATUS with port_mutex
The patch fixes a problem in the lp driver that can cause oopses as follows: process A: calls lp_write, which in turn calls parport_ieee1284_write_compat, and that invokes parport_wait_peripheral process B: meanwhile does an ioctl(LPGETSTATUS), which call lp_release_parport when done. This function will set physport->cad = NULL. process A: parport_wait_peripheral tries to dereference physport->cad and dies So, protect that code with the port_mutex in order to protect against simultaneous calls to lp_read/lp_write. Similar protection is probably required for ioctl(LPRESET)... This patch was done by IBM a while back and we (at suse) have that since at least 2004 in our repos. Let's make it upstream. Signed-off-by: okir@suse.de Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -622,9 +622,12 @@ static int lp_do_ioctl(unsigned int minor, unsigned int cmd,
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return -EFAULT;
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break;
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case LPGETSTATUS:
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if (mutex_lock_interruptible(&lp_table[minor].port_mutex))
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return -EINTR;
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lp_claim_parport_or_block (&lp_table[minor]);
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status = r_str(minor);
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lp_release_parport (&lp_table[minor]);
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mutex_unlock(&lp_table[minor].port_mutex);
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if (copy_to_user(argp, &status, sizeof(int)))
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return -EFAULT;
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