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

Pasha Tatashin
2022-05-27T02:55:56Z

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@soleen.com>
---
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