lib: move strncpy_from_unsafe() into mm/maccess.c
To fix build errors:
kernel/built-in.o: In function `bpf_trace_printk':
bpf_trace.c:(.text+0x11a254): undefined reference to `strncpy_from_unsafe'
kernel/built-in.o: In function `fetch_memory_string':
trace_kprobe.c:(.text+0x11acf8): undefined reference to `strncpy_from_unsafe'
move strncpy_from_unsafe() next to probe_kernel_read/write()
which use the same memory access style.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 1a6877b9c0c2 ("lib: introduce strncpy_from_unsafe()")
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/mm/maccess.c b/mm/maccess.c
index d53adf9..34fe247 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -60,3 +60,44 @@
return ret ? -EFAULT : 0;
}
EXPORT_SYMBOL_GPL(probe_kernel_write);
+
+/**
+ * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.
+ * @dst: Destination address, in kernel space. This buffer must be at
+ * least @count bytes long.
+ * @src: Unsafe address.
+ * @count: Maximum number of bytes to copy, including the trailing NUL.
+ *
+ * Copies a NUL-terminated string from unsafe address to kernel buffer.
+ *
+ * On success, returns the length of the string INCLUDING the trailing NUL.
+ *
+ * If access fails, returns -EFAULT (some data may have been copied
+ * and the trailing NUL added).
+ *
+ * If @count is smaller than the length of the string, copies @count-1 bytes,
+ * sets the last byte of @dst buffer to NUL and returns @count.
+ */
+long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
+{
+ mm_segment_t old_fs = get_fs();
+ const void *src = unsafe_addr;
+ long ret;
+
+ if (unlikely(count <= 0))
+ return 0;
+
+ set_fs(KERNEL_DS);
+ pagefault_disable();
+
+ do {
+ ret = __copy_from_user_inatomic(dst++,
+ (const void __user __force *)src++, 1);
+ } while (dst[-1] && ret == 0 && src - unsafe_addr < count);
+
+ dst[-1] = '\0';
+ pagefault_enable();
+ set_fs(old_fs);
+
+ return ret < 0 ? ret : src - unsafe_addr;
+}