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

Baoquan He
2022-06-08T04:48:26Z

On 05/27/22 at 02:55am, Pasha Tatashin wrote:
> 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.

LGTM,

Acked-by: Baoquan He <bhe@redhat.com>

>
> 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
>