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

Pasha Tatashin
2022-06-07T15:54:11Z

On Sun, Jun 5, 2022 at 10:45 PM Baoquan He <bhe@redhat.com> wrote:
>
> 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.
>
> If we really met initramfs bigger than 2G, it's reasonable to increase
> the limit. While wondering why we should take sszie_t, but not size_t.

ssize_t instead of size_t so we can return errors as negative values.

Pasha

>
> >
> > 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
> >
>