`do_cmd_ioctl()` in "comedi_fops.c" handles the `COMEDI_CMD` ioctl. This returns `-EAGAIN` if it has copied a modified `struct comedi_cmd` back to user-space. (This occurs when the low-level Comedi driver's `do_cmdtest()` handler returns non-zero to indicate a problem with the contents of the `struct comedi_cmd`, or when the `struct comedi_cmd` has the `CMDF_BOGUS` flag set.) `compat_cmd()` in "comedi_compat32.c" handles the 32-bit compatible version of the `COMEDI_CMD` ioctl. Currently, it never copies a 32-bit compatible version of `struct comedi_cmd` back to user-space, which is at odds with the way the regular `COMEDI_CMD` ioctl is handled. To fix it, change `compat_cmd()` to copy a 32-bit compatible version of the `struct comedi_cmd` back to user-space when the main ioctl handler returns `-EAGAIN`. Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> --- v2: keep existing type of `rc` variable - don't change it to `long`. --- drivers/staging/comedi/comedi_compat32.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/staging/comedi/comedi_compat32.c b/drivers/staging/comedi/comedi_compat32.c index 5a4c74f..03a2d07 100644 --- a/drivers/staging/comedi/comedi_compat32.c +++ b/drivers/staging/comedi/comedi_compat32.c @@ -262,7 +262,7 @@ static int compat_cmd(struct file *file, unsigned long arg) { struct comedi_cmd __user *cmd; struct comedi32_cmd_struct __user *cmd32; - int rc; + int rc, err; cmd32 = compat_ptr(arg); cmd = compat_alloc_user_space(sizeof(*cmd)); @@ -271,7 +271,15 @@ static int compat_cmd(struct file *file, unsigned long arg) if (rc) return rc; - return translated_ioctl(file, COMEDI_CMD, (unsigned long)cmd); + rc = translated_ioctl(file, COMEDI_CMD, (unsigned long)cmd); + if (rc == -EAGAIN) { + /* Special case: copy cmd back to user. */ + err = put_compat_cmd(cmd32, cmd); + if (err) + rc = err; + } + + return rc; } /* Handle 32-bit COMEDI_CMDTEST ioctl. */ -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html