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POWhy does copying a struct from user space fails in an ioctl command?
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  1. POWhy does copying a struct from user space fails in an ioctl command?
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    copied!<p>I'm developing a device driver and need to make use of IOCTL. Unfortunately I cannot copy a struct from user space. Here is the code (simplified, error handling removed):</p> <p><strong>Structure</strong></p> <pre><code>struct secvault_createoptions { int secvaultId; long dataSize; char key[SECVAULT_KEYSIZE]; }; </code></pre> <p><strong>Application</strong></p> <pre><code>void createSecvault(int secvaultId) { struct secvault_createoptions creationOptions; /* fill with data */ sendIoctlCommand(SECVAULT_IOCTL_CREATE, &amp;creationOptions); } void sendIoctlCommand(int command, void *arg) { FILE *stream; int fd, err; stream = fopen(SECVAULT_DEV_CONTROL, "r"); fd = fileno(stream); ioctl(fd, command, arg); fclose(stream); } </code></pre> <p><strong>Kernel Module</strong></p> <pre><code>int control_device_ioctl(struct inode *node, struct file *filp, unsigned int cmd, unsigned long arg) { struct secvault_createoptions creationOptions; int returnCode; switch (cmd) { case SECVAULT_IOCTL_CREATE: if (copy_from_user(&amp;creationOptions, (void*)arg, sizeof(struct secvault_createoptions)) != sizeof(struct secvault_createoptions)) { /* Always this branch gets executed */ printk(KERN_ALERT "Copying secure vault creation options from user space failed.\n"); returnCode = -EFAULT; break; } printk(KERN_ALERT "2 IOCTL create request on control device received: secvaultId = %d, dataSize = %ld.\n", creationOptions.secvaultId, creationOptions.dataSize); returnCode = createDataDevice(&amp;creationOptions); break; } return returnCode; } </code></pre> <p>Best Regards,<br> Oliver Hanappi</p>
 

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