Some low-level comedi drivers (incorrectly) point `dev->read_subdev` or `dev->write_subdev` to a subdevice that does not support asynchronous commands. Comedi's poll(), read() and write() file operation handlers assume these subdevices do support asynchronous commands. In particular, they assume `s->async` is valid (where `s` points to the read or write subdevice), which it won't be if it has been set incorrectly. This can lead to a NULL pointer dereference.
Check `s->async` is non-NULL in `comedi_poll()`, `comedi_read()` and `comedi_write()` to avoid the bug. Signed-off-by: Ian Abbott <[email protected]> --- Note: this patch is for staging-next. Needs backporting for earlier kernels. --- drivers/staging/comedi/comedi_fops.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index c7377d0..4a28d75 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -1844,7 +1844,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait) } s = comedi_read_subdevice(info); - if (s) { + if (s && s->async) { poll_wait(file, &s->async->wait_head, wait); if (!s->busy || !comedi_is_subdevice_running(s) || comedi_buf_read_n_available(s->async) > 0) @@ -1852,7 +1852,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait) } s = comedi_write_subdevice(info); - if (s) { + if (s && s->async) { unsigned int bps = bytes_per_sample(s->async->subdevice); poll_wait(file, &s->async->wait_head, wait); @@ -1887,7 +1887,7 @@ static ssize_t comedi_write(struct file *file, const char __user *buf, } s = comedi_write_subdevice(info); - if (!s) + if (!s || !s->async) return -EIO; async = s->async; @@ -1982,7 +1982,7 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes, } s = comedi_read_subdevice(info); - if (!s) + if (!s || !s->async) return -EIO; async = s->async; -- 1.8.1.2 _______________________________________________ devel mailing list [email protected] http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
