[PATCH v2 1/2] fs/kernel_read_file: Allow to read files up-to ssize_t

[Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>]

Currently, the maximum file size that is supported is 2G. This may be
too small in some cases. For example, kexec_file_load() system call
loads initramfs. In some netboot cases initramfs can be rather large.

Allow to use up-to ssize_t bytes. The callers still can limit the
maximum file size via buf_size.

Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
---
 fs/kernel_read_file.c            | 38 ++++++++++++++++----------------
 include/linux/kernel_read_file.h | 32 +++++++++++++--------------
 include/linux/limits.h           |  1 +
 3 files changed, 36 insertions(+), 35 deletions(-)

diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c
index 1b07550485b9..5d826274570c 100644
--- a/fs/kernel_read_file.c
+++ b/fs/kernel_read_file.c
@@ -29,15 +29,15 @@
  * change between calls to kernel_read_file().
  *
  * Returns number of bytes read (no single read will be bigger
- * than INT_MAX), or negative on error.
+ * than SSIZE_MAX), or negative on error.
  *
  */
-int kernel_read_file(struct file *file, loff_t offset, void **buf,
-		     size_t buf_size, size_t *file_size,
-		     enum kernel_read_file_id id)
+ssize_t kernel_read_file(struct file *file, loff_t offset, void **buf,
+			 size_t buf_size, size_t *file_size,
+			 enum kernel_read_file_id id)
 {
 	loff_t i_size, pos;
-	size_t copied;
+	ssize_t copied;
 	void *allocated = NULL;
 	bool whole_file;
 	int ret;
@@ -58,7 +58,7 @@ int kernel_read_file(struct file *file, loff_t offset, void **buf,
 		goto out;
 	}
 	/* The file is too big for sane activities. */
-	if (i_size > INT_MAX) {
+	if (i_size > SSIZE_MAX) {
 		ret = -EFBIG;
 		goto out;
 	}
@@ -124,12 +124,12 @@ int kernel_read_file(struct file *file, loff_t offset, void **buf,
 }
 EXPORT_SYMBOL_GPL(kernel_read_file);
 
-int kernel_read_file_from_path(const char *path, loff_t offset, void **buf,
-			       size_t buf_size, size_t *file_size,
-			       enum kernel_read_file_id id)
+ssize_t kernel_read_file_from_path(const char *path, loff_t offset, void **buf,
+				   size_t buf_size, size_t *file_size,
+				   enum kernel_read_file_id id)
 {
 	struct file *file;
-	int ret;
+	ssize_t ret;
 
 	if (!path || !*path)
 		return -EINVAL;
@@ -144,14 +144,14 @@ int kernel_read_file_from_path(const char *path, loff_t offset, void **buf,
 }
 EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
 
-int kernel_read_file_from_path_initns(const char *path, loff_t offset,
-				      void **buf, size_t buf_size,
-				      size_t *file_size,
-				      enum kernel_read_file_id id)
+ssize_t kernel_read_file_from_path_initns(const char *path, loff_t offset,
+					  void **buf, size_t buf_size,
+					  size_t *file_size,
+					  enum kernel_read_file_id id)
 {
 	struct file *file;
 	struct path root;
-	int ret;
+	ssize_t ret;
 
 	if (!path || !*path)
 		return -EINVAL;
@@ -171,12 +171,12 @@ int kernel_read_file_from_path_initns(const char *path, loff_t offset,
 }
 EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);
 
-int kernel_read_file_from_fd(int fd, loff_t offset, void **buf,
-			     size_t buf_size, size_t *file_size,
-			     enum kernel_read_file_id id)
+ssize_t kernel_read_file_from_fd(int fd, loff_t offset, void **buf,
+				 size_t buf_size, size_t *file_size,
+				 enum kernel_read_file_id id)
 {
 	struct fd f = fdget(fd);
-	int ret = -EBADF;
+	ssize_t ret = -EBADF;
 
 	if (!f.file || !(f.file->f_mode & FMODE_READ))
 		goto out;
diff --git a/include/linux/kernel_read_file.h b/include/linux/kernel_read_file.h
index 575ffa1031d3..90451e2e12bd 100644
--- a/include/linux/kernel_read_file.h
+++ b/include/linux/kernel_read_file.h
@@ -35,21 +35,21 @@ static inline const char *kernel_read_file_id_str(enum kernel_read_file_id id)
 	return kernel_read_file_str[id];
 }
 
-int kernel_read_file(struct file *file, loff_t offset,
-		     void **buf, size_t buf_size,
-		     size_t *file_size,
-		     enum kernel_read_file_id id);
-int kernel_read_file_from_path(const char *path, loff_t offset,
-			       void **buf, size_t buf_size,
-			       size_t *file_size,
-			       enum kernel_read_file_id id);
-int kernel_read_file_from_path_initns(const char *path, loff_t offset,
-				      void **buf, size_t buf_size,
-				      size_t *file_size,
-				      enum kernel_read_file_id id);
-int kernel_read_file_from_fd(int fd, loff_t offset,
-			     void **buf, size_t buf_size,
-			     size_t *file_size,
-			     enum kernel_read_file_id id);
+ssize_t kernel_read_file(struct file *file, loff_t offset,
+			 void **buf, size_t buf_size,
+			 size_t *file_size,
+			 enum kernel_read_file_id id);
+ssize_t kernel_read_file_from_path(const char *path, loff_t offset,
+				   void **buf, size_t buf_size,
+				   size_t *file_size,
+				   enum kernel_read_file_id id);
+ssize_t kernel_read_file_from_path_initns(const char *path, loff_t offset,
+					  void **buf, size_t buf_size,
+					  size_t *file_size,
+					  enum kernel_read_file_id id);
+ssize_t kernel_read_file_from_fd(int fd, loff_t offset,
+				 void **buf, size_t buf_size,
+				 size_t *file_size,
+				 enum kernel_read_file_id id);
 
 #endif /* _LINUX_KERNEL_READ_FILE_H */
diff --git a/include/linux/limits.h b/include/linux/limits.h
index b568b9c30bbf..f6bcc9369010 100644
--- a/include/linux/limits.h
+++ b/include/linux/limits.h
@@ -7,6 +7,7 @@
 #include <vdso/limits.h>
 
 #define SIZE_MAX	(~(size_t)0)
+#define SSIZE_MAX	((ssize_t)(SIZE_MAX >> 1))
 #define PHYS_ADDR_MAX	(~(phys_addr_t)0)
 
 #define U8_MAX		((u8)~0U)
-- 
2.36.1.124.g0e6072fb45-goog