[PATCH v2 0/2] Allow to kexec with initramfs larger than 2G

[PATCH v2 0/2] Allow to kexec with initramfs larger than 2G

[Pasha Tatashin]

Currently, the largest initramfs that is supported by kexec_file_load()
syscall is 2G.

This is because kernel_read_file() returns int, and is limited to
INT_MAX or 2G.

On the other hand, there are kexec based boot loaders (i.e. u-root),
that may need to boot netboot images that might be larger than 2G.

The first patch changes the return type from int to ssize_t in
kernel_read_file* functions.

The second patch increases the maximum initramfs file size to 4G.

Tested: verified that can kexec_file_load() works with 4G initramfs
on x86_64.

Pasha Tatashin (2):
  fs/kernel_read_file: Allow to read files up-to ssize_t
  kexec_file: Increase maximum file size to 4G

 fs/kernel_read_file.c            | 38 ++++++++++++++++----------------
 include/linux/kernel_read_file.h | 32 +++++++++++++--------------
 include/linux/limits.h           |  1 +
 kernel/kexec_file.c              | 10 ++++++---
 4 files changed, 43 insertions(+), 38 deletions(-)

-- 
2.36.1.124.g0e6072fb45-goog

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

[Pasha Tatashin]

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

[PATCH v2 2/2] kexec_file: Increase maximum file size to 4G

[Pasha Tatashin]

In some case initrd can be large. For example, it could be a netboot
image loaded by u-root, that is kexec'ing into it.

The maximum size of initrd is arbitrary set to 2G. Also, the limit is
not very obvious because it is hidden behind a generic INT_MAX macro.

Theoretically, we could make it LONG_MAX, but it is safer to keep it
sane, and just increase it to 4G.

Increase the size to 4G, and make it obvious by having a new macro
that specifies the maximum file size supported by kexec_file_load()
syscall: KEXEC_FILE_SIZE_MAX.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 kernel/kexec_file.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 8347fc158d2b..f00cf70d82b9 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -31,6 +31,9 @@
 
 static int kexec_calculate_store_digests(struct kimage *image);
 
+/* Maximum size in bytes for kernel/initrd files. */
+#define KEXEC_FILE_SIZE_MAX	min_t(s64, 4LL << 30, SSIZE_MAX)
+
 /*
  * Currently this is the only default function that is exported as some
  * architectures need it to do additional handlings.
@@ -223,11 +226,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 			     const char __user *cmdline_ptr,
 			     unsigned long cmdline_len, unsigned flags)
 {
-	int ret;
+	ssize_t ret;
 	void *ldata;
 
 	ret = kernel_read_file_from_fd(kernel_fd, 0, &image->kernel_buf,
-				       INT_MAX, NULL, READING_KEXEC_IMAGE);
+				       KEXEC_FILE_SIZE_MAX, NULL,
+				       READING_KEXEC_IMAGE);
 	if (ret < 0)
 		return ret;
 	image->kernel_buf_len = ret;
@@ -247,7 +251,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 	/* It is possible that there no initramfs is being loaded */
 	if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
 		ret = kernel_read_file_from_fd(initrd_fd, 0, &image->initrd_buf,
-					       INT_MAX, NULL,
+					       KEXEC_FILE_SIZE_MAX, NULL,
 					       READING_KEXEC_INITRAMFS);
 		if (ret < 0)
 			goto out;
-- 
2.36.1.124.g0e6072fb45-goog

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

[Baoquan He]

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.

> 
> 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
> 


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Re: [PATCH v2 2/2] kexec_file: Increase maximum file size to 4G

[Baoquan He]

On 05/27/22 at 02:55am, Pasha Tatashin wrote:
> In some case initrd can be large. For example, it could be a netboot
> image loaded by u-root, that is kexec'ing into it.
> 
> The maximum size of initrd is arbitrary set to 2G. Also, the limit is
> not very obvious because it is hidden behind a generic INT_MAX macro.
> 
> Theoretically, we could make it LONG_MAX, but it is safer to keep it
> sane, and just increase it to 4G.

Do we need to care about 32bit system where initramfs could be larger
than 2G? On 32bit system, SSIZE_MAX is still 2G, right?

Another concern is if 2G is enough. If we can foresee it might need be
enlarged again in a near future, LONG_MAX certainly is not a good
value, but a little bigger multiple of 2G can be better?

> 
> Increase the size to 4G, and make it obvious by having a new macro
> that specifies the maximum file size supported by kexec_file_load()
> syscall: KEXEC_FILE_SIZE_MAX.
> 
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> ---
>  kernel/kexec_file.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index 8347fc158d2b..f00cf70d82b9 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -31,6 +31,9 @@
>  
>  static int kexec_calculate_store_digests(struct kimage *image);
>  
> +/* Maximum size in bytes for kernel/initrd files. */
> +#define KEXEC_FILE_SIZE_MAX	min_t(s64, 4LL << 30, SSIZE_MAX)
> +
>  /*
>   * Currently this is the only default function that is exported as some
>   * architectures need it to do additional handlings.
> @@ -223,11 +226,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
>  			     const char __user *cmdline_ptr,
>  			     unsigned long cmdline_len, unsigned flags)
>  {
> -	int ret;
> +	ssize_t ret;
>  	void *ldata;
>  
>  	ret = kernel_read_file_from_fd(kernel_fd, 0, &image->kernel_buf,
> -				       INT_MAX, NULL, READING_KEXEC_IMAGE);
> +				       KEXEC_FILE_SIZE_MAX, NULL,
> +				       READING_KEXEC_IMAGE);
>  	if (ret < 0)
>  		return ret;
>  	image->kernel_buf_len = ret;
> @@ -247,7 +251,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
>  	/* It is possible that there no initramfs is being loaded */
>  	if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
>  		ret = kernel_read_file_from_fd(initrd_fd, 0, &image->initrd_buf,
> -					       INT_MAX, NULL,
> +					       KEXEC_FILE_SIZE_MAX, NULL,
>  					       READING_KEXEC_INITRAMFS);
>  		if (ret < 0)
>  			goto out;
> -- 
> 2.36.1.124.g0e6072fb45-goog
> 


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

[Pasha Tatashin]

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
> >
>

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Re: [PATCH v2 2/2] kexec_file: Increase maximum file size to 4G

[Pasha Tatashin]

On Sun, Jun 5, 2022 at 10:56 PM Baoquan He <bhe@redhat.com> wrote:
>
> On 05/27/22 at 02:55am, Pasha Tatashin wrote:
> > In some case initrd can be large. For example, it could be a netboot
> > image loaded by u-root, that is kexec'ing into it.
> >
> > The maximum size of initrd is arbitrary set to 2G. Also, the limit is
> > not very obvious because it is hidden behind a generic INT_MAX macro.
> >
> > Theoretically, we could make it LONG_MAX, but it is safer to keep it
> > sane, and just increase it to 4G.
>
> Do we need to care about 32bit system where initramfs could be larger
> than 2G? On 32bit system, SSIZE_MAX is still 2G, right?

Yes, on 32-bit SSIZE_MAX is still 2G, so we are safe to keep 32-bit
systems run exactly as today.

#define KEXEC_FILE_SIZE_MAX    min_t(s64, 4LL << 30, SSIZE_MAX)
Is meant to protect against running over the 2G limit on 32-bit systems.

>
> Another concern is if 2G is enough. If we can foresee it might need be
> enlarged again in a near future, LONG_MAX certainly is not a good
> value, but a little bigger multiple of 2G can be better?

This little series enables increasing the max value above 2G, but
still keeps it within a sane size i.e. 4G, If 4G seems too small, I
can change it to 8G or 16G instead of 4G.

Thanks,
Pasha

>
> >
> > Increase the size to 4G, and make it obvious by having a new macro
> > that specifies the maximum file size supported by kexec_file_load()
> > syscall: KEXEC_FILE_SIZE_MAX.
> >
> > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> > ---
> >  kernel/kexec_file.c | 10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> > index 8347fc158d2b..f00cf70d82b9 100644
> > --- a/kernel/kexec_file.c
> > +++ b/kernel/kexec_file.c
> > @@ -31,6 +31,9 @@
> >
> >  static int kexec_calculate_store_digests(struct kimage *image);
> >
> > +/* Maximum size in bytes for kernel/initrd files. */
> > +#define KEXEC_FILE_SIZE_MAX  min_t(s64, 4LL << 30, SSIZE_MAX)
> > +
> >  /*
> >   * Currently this is the only default function that is exported as some
> >   * architectures need it to do additional handlings.
> > @@ -223,11 +226,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
> >                            const char __user *cmdline_ptr,
> >                            unsigned long cmdline_len, unsigned flags)
> >  {
> > -     int ret;
> > +     ssize_t ret;
> >       void *ldata;
> >
> >       ret = kernel_read_file_from_fd(kernel_fd, 0, &image->kernel_buf,
> > -                                    INT_MAX, NULL, READING_KEXEC_IMAGE);
> > +                                    KEXEC_FILE_SIZE_MAX, NULL,
> > +                                    READING_KEXEC_IMAGE);
> >       if (ret < 0)
> >               return ret;
> >       image->kernel_buf_len = ret;
> > @@ -247,7 +251,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
> >       /* It is possible that there no initramfs is being loaded */
> >       if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
> >               ret = kernel_read_file_from_fd(initrd_fd, 0, &image->initrd_buf,
> > -                                            INT_MAX, NULL,
> > +                                            KEXEC_FILE_SIZE_MAX, NULL,
> >                                              READING_KEXEC_INITRAMFS);
> >               if (ret < 0)
> >                       goto out;
> > --
> > 2.36.1.124.g0e6072fb45-goog
> >
>

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Re: [PATCH v2 2/2] kexec_file: Increase maximum file size to 4G

[Baoquan He]

On 06/07/22 at 12:02pm, Pasha Tatashin wrote:
> On Sun, Jun 5, 2022 at 10:56 PM Baoquan He <bhe@redhat.com> wrote:
> >
> > On 05/27/22 at 02:55am, Pasha Tatashin wrote:
> > > In some case initrd can be large. For example, it could be a netboot
> > > image loaded by u-root, that is kexec'ing into it.
> > >
> > > The maximum size of initrd is arbitrary set to 2G. Also, the limit is
> > > not very obvious because it is hidden behind a generic INT_MAX macro.
> > >
> > > Theoretically, we could make it LONG_MAX, but it is safer to keep it
> > > sane, and just increase it to 4G.
> >
> > Do we need to care about 32bit system where initramfs could be larger
> > than 2G? On 32bit system, SSIZE_MAX is still 2G, right?
> 
> Yes, on 32-bit SSIZE_MAX is still 2G, so we are safe to keep 32-bit
> systems run exactly as today.
> 
> #define KEXEC_FILE_SIZE_MAX    min_t(s64, 4LL << 30, SSIZE_MAX)
> Is meant to protect against running over the 2G limit on 32-bit systems.

OK. In fact I was wrong. I386 doesn't have kexec_file loading support.

> 
> >
> > Another concern is if 2G is enough. If we can foresee it might need be
                          ~~ 4G, typo
> > enlarged again in a near future, LONG_MAX certainly is not a good
> > value, but a little bigger multiple of 2G can be better?
> 
> This little series enables increasing the max value above 2G, but
> still keeps it within a sane size i.e. 4G, If 4G seems too small, I
> can change it to 8G or 16G instead of 4G.

Just raising to try to discuss if 4G is enough. I have no knowledge
about how much is enough, and we don't need to guess, if you think 4G is
enough according to information you get, that's OK. We can wait a while
to see if other people have words about the vlaue. If no, then 4G is a
good one.

Thanks
Baoquan


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

[Baoquan He]

On 06/07/22 at 11:52am, Pasha Tatashin wrote:
> 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.

Makes sense. Thanks.


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

[Baoquan He]

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
> 


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