lkml.org 
[lkml]   [2017]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH] block: sed-opal: reduce stack size of ioctl handler
Date
From: Arnd Bergmann
> Sent: 08 February 2017 21:15
>
> When CONFIG_KASAN is in use, the sed_ioctl function uses unusually large stack,
> as each possible ioctl argument gets its own stack area plus redzone:

Why not do a single copy_from_user() at the top of sed_ioctl() based on
the _IOC_DIR() and __IOC_SIZE() values?

Something like:
int sed_ioctl(..., unsigned int cmd, void __user *arg)
{
u64 buf[??]; /* or a union */
unsigned int cmd_sz = _IOC_SIZE(cmd);

if (_IOC_DIR(cmd) & (_IOC_WRITE | _IOC_READ) && cmd_sz > sizeof buf)
return -EINVAL;

if (_IOC_DIR(cmd) & _IOC_WRITE) {
if (copy_from_user(buf, arg, cmd_sz))
return -EFAULT;
} else {
if (IOC_DIR(cmd) & _IOC_READ))
memzero(buf, cmd_sz);
}

switch (cmd) {
...
rval = ...
...
}

if (rval >= 0 && (_IOC_DIR(cmd) & _IOC_READ)
&& copy_to_user(arg, buf, cmd_sz));
return -EFAULT;

return rval;
}

David

\
 
 \ /
  Last update: 2017-02-09 15:26    [W:0.049 / U:0.212 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site