module/decompress: use kvmalloc() consistently

We consistently switched from kmalloc() to vmalloc() in module
decompression to prevent potential memory allocation failures with large
modules, however vmalloc() is not as memory-efficient and fast as
kmalloc().

Since we don't know in general the size of the workspace required by the
decompression algorithm, it is more reasonable to use kvmalloc()
consistently, also considering that we don't have special memory
requirements here.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Tested-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Andrea Righi

kernel/module/decompress.c

@@ -100,7 +100,7 @@ static ssize_t module_gzip_decompress(struct load_info *info,
 	s.next_in = buf + gzip_hdr_len;
 	s.avail_in = size - gzip_hdr_len;
 
-	s.workspace = vmalloc(zlib_inflate_workspacesize());
+	s.workspace = kvmalloc(zlib_inflate_workspacesize(), GFP_KERNEL);
 	if (!s.workspace)
 		return -ENOMEM;
 
@@ -138,7 +138,7 @@ static ssize_t module_gzip_decompress(struct load_info *info,
 out_inflate_end:
 	zlib_inflateEnd(&s);
 out:
-	vfree(s.workspace);
+	kvfree(s.workspace);
 	return retval;
 }
 #elif defined(CONFIG_MODULE_COMPRESS_XZ)
@@ -241,7 +241,7 @@ static ssize_t module_zstd_decompress(struct load_info *info,
 	}
 
 	wksp_size = zstd_dstream_workspace_bound(header.windowSize);
-	wksp = vmalloc(wksp_size);
+	wksp = kvmalloc(wksp_size, GFP_KERNEL);
 	if (!wksp) {
 		retval = -ENOMEM;
 		goto out;
@@ -284,7 +284,7 @@ static ssize_t module_zstd_decompress(struct load_info *info,
 	retval = new_size;
 
  out:
-	vfree(wksp);
+	kvfree(wksp);
 	return retval;
 }
 #else