Re: [PATCH V3 2/2] Move stack parameters for sed_ioctl to prevent oversized stack with CONFIG_KASAN

From: Johannes Thumshirn
Date: Fri Feb 10 2017 - 02:47:58 EST


On 02/09/2017 06:20 PM, Scott Bauer wrote:
> When CONFIG_KASAN is enabled, compilation fails:
>
> block/sed-opal.c: In function 'sed_ioctl':
> block/sed-opal.c:2447:1: error: the frame size of 2256 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
>
> Moved all the ioctl structures off the stack and dynamically activate
> using _IOC_SIZE()
>
> Fixes: 455a7b238cd6 ("block: Add Sed-opal library")
>
> Reported-by: Arnd Bergmann <arnd@xxxxxxxx>
> Signed-off-by: Scott Bauer <scott.bauer@xxxxxxxxx>
> ---
> block/sed-opal.c | 134 +++++++++++++++++++++----------------------------------
> 1 file changed, 50 insertions(+), 84 deletions(-)
>

[...]

> - if (copy_from_user(&session, arg, sizeof(session)))
> - return -EFAULT;
> - return opal_erase_locking_range(dev, &session);
> + ioctl_ptr = kzalloc(cmd_size, GFP_KERNEL);
> + if (!ioctl_ptr)
> + return -ENOMEM;
> + if (copy_from_user(ioctl_ptr, arg, cmd_size)) {
> + ret = -EFAULT;
> + goto out;
> }

Can't we use memdup_user() instead of kzalloc() + copy_from_user()?



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