This was added to the mainline kernel in commit 3bc8f29b14 "new helper:
memdup_user_nul()" and is now used by multiple drivers.
Signed-off-by: Hauke Mehrtens <hauke@xxxxxxxxxx>
---
backport/backport-include/linux/string.h | 5 +++++
backport/compat/backport-4.5.c | 34 ++++++++++++++++++++++++++++++++
2 files changed, 39 insertions(+)
diff --git a/backport/backport-include/linux/string.h b/backport/backport-include/linux/string.h
index 819d141..878d033 100644
--- a/backport/backport-include/linux/string.h
+++ b/backport/backport-include/linux/string.h
@@ -8,4 +8,9 @@
extern size_t memweight(const void *ptr, size_t bytes);
#endif
+#if (LINUX_VERSION_CODE < KERNEL_VERSION(4,5,0))
+#define memdup_user_nul LINUX_BACKPORT(memdup_user_nul)
+extern void *memdup_user_nul(const void __user *, size_t);
+#endif
+
#endif /* __BACKPORT_LINUX_STRING_H */
diff --git a/backport/compat/backport-4.5.c b/backport/compat/backport-4.5.c
index 13c0a71..b7e6da0 100644
--- a/backport/compat/backport-4.5.c
+++ b/backport/compat/backport-4.5.c
@@ -12,6 +12,9 @@
#include <linux/export.h>
#include <linux/errno.h>
#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <asm/uaccess.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,19,0)
int led_set_brightness_sync(struct led_classdev *led_cdev,
@@ -58,3 +61,34 @@ loff_t no_seek_end_llseek(struct file *file, loff_t offset, int whence)
}
EXPORT_SYMBOL_GPL(no_seek_end_llseek);
#endif /* >= 3.2 */
+
+/**
+ * memdup_user_nul - duplicate memory region from user space and NUL-terminate
+ *
+ * @src: source address in user space
+ * @len: number of bytes to copy
+ *
+ * Returns an ERR_PTR() on failure.
+ */
+void *memdup_user_nul(const void __user *src, size_t len)
+{
+ char *p;
+
+ /*
+ * Always use GFP_KERNEL, since copy_from_user() can sleep and
+ * cause pagefault, which makes it pointless to use GFP_NOFS
+ * or GFP_ATOMIC.
+ */
+ p = kmalloc(len + 1, GFP_KERNEL);
+ if (!p)
+ return ERR_PTR(-ENOMEM);
+
+ if (copy_from_user(p, src, len)) {
+ kfree(p);
+ return ERR_PTR(-EFAULT);
+ }
+ p[len] = '\0';
+
+ return p;
+}
+EXPORT_SYMBOL_GPL(memdup_user_nul);
--
2.7.0
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