RE: [PATCH 07/13] fs/kernel_read_file: Switch buffer size arg to size_t

Sent: 17 July 2020 18:43
In preparation for further refactoring of kernel_read_file*(), rename
the "max_size" argument to the more accurate "buf_size", and correct
its type to size_t. Add kerndoc to explain the specifics of how the
arguments will be used. Note that with buf_size now size_t, it can no
longer be negative (and was never called with a negative value). Adjust
callers to use it as a "maximum size" when *buf is NULL.

Signed-off-by: Kees Cook <redacted>
---
 fs/kernel_read_file.c            | 34 +++++++++++++++++++++++---------
 include/linux/kernel_read_file.h |  8 ++++----
 security/integrity/digsig.c      |  2 +-
 security/integrity/ima/ima_fs.c  |  2 +-
 4 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c
index dc28a8def597..e21a76001fff 100644
--- a/fs/kernel_read_file.c
+++ b/fs/kernel_read_file.c

@@ -5,15 +5,31 @@
 #include <linux/security.h>
 #include <linux/vmalloc.h>

+/**
+ * kernel_read_file() - read file contents into a kernel buffer
+ *
+ * @file	file to read from
+ * @buf		pointer to a "void *" buffer for reading into (if
+ *		*@buf is NULL, a buffer will be allocated, and
+ *		@buf_size will be ignored)
+ * @buf_size	size of buf, if already allocated. If @buf not
+ *		allocated, this is the largest size to allocate.
+ * @id		the kernel_read_file_id identifying the type of
+ *		file contents being read (for LSMs to examine)
+ *
+ * Returns number of bytes read (no single read will be bigger
+ * than INT_MAX), or negative on error.
+ *
+ */