CODEWITHSUNDEEP
linuxmodulekernelchainingioctl
zenbooster
zenbooster

Reputation: 29

How to call ioctl from kernel space in Linux kernel 5.10?

My driver's IOCTL handler redirects IOCTL requests to another driver. This used to work great, but when I needed to add support for the 5.10 kernel, it turned out that the old way didn't work anymore. How can this be done now?

#define TARGET_ID "TGT"
// ...
char id[sizeof(TARGET_ID)];
// ...
mm_segment_t old_fs = get_fs();
set_fs(KERNEL_DS);
res = __blkdev_driver_ioctl(dev->bdev_raw, 0, SCSI_IOCTL_TARGET_ID, (unsigned long)id);
set_fs(old_fs);

if(0 == strcmp(id, TARGET_ID))
{
    PINFO("*** target driver detected! ***\n");
    dev->is_target_driver = true;
}
else
{
    ...

Upvotes: 0

Views: 892

Answers (2)

T.Cris
T.Cris

Reputation: 63

It seems like that force_uaccess_begin() cannot replace set_fs(KERNEL_DS); Below is its definition:

static inline mm_segment_t force_uaccess_begin(void)
{
    mm_segment_t fs = get_fs();

    set_fs(USER_DS);
    return fs;
}

And mm_segment_t, force_uaccess_begin all have been removed after linux 5.18.

Upvotes: 1

zenbooster
zenbooster

Reputation: 29

Hooray! Hooray! Hooray! ;) This is how it will work:

    #define TARGET_ID "TGT"
    // ...
    char id[sizeof(TARGET_ID)];
    // ...
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 15, 4)
    mm_segment_t old_fs = force_uaccess_begin();
    res = __blkdev_driver_ioctl(dev->bdev_raw, 0, SCSI_IOCTL_TARGET_ID, (unsigned long)id);
    force_uaccess_end(old_fs);
#else
    mm_segment_t old_fs = get_fs();
    set_fs(KERNEL_DS);
    res = __blkdev_driver_ioctl(dev->bdev_raw, 0, SCSI_IOCTL_TARGET_ID, (unsigned long)id);
    set_fs(old_fs);
#endif
    
    if(0 == strcmp(id, TARGET_ID))
    {
        PINFO("*** target driver detected! ***\n");
        dev->is_target_driver = true;
    }
    else
    {
        ...

Upvotes: 1

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