fs/kernel_read_file: allow to read files up-to ssize_t

Patch series "Allow to kexec with initramfs larger than 2G", v2.

Currently, the largest initramfs that is supported by kexec_file_load()
sysca

fs/kernel_read_file: allow to read files up-to ssize_t

Patch series "Allow to kexec with initramfs larger than 2G", v2.

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.


This patch (of 2):

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.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Pasha Tatashin <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Greg Thelen <[email protected]>
Cc: Sasha Levin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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fs/kernel_file_read: Add "offset" arg for partial reads

To perform partial reads, callers of kernel_read_file*() must have a
non-NULL file_size argument and a preallocated buffer. The new "offset"
a

fs/kernel_file_read: Add "offset" arg for partial reads

To perform partial reads, callers of kernel_read_file*() must have a
non-NULL file_size argument and a preallocated buffer. The new "offset"
argument can then be used to seek to specific locations in the file to
fill the buffer to, at most, "buf_size" per call.

Where possible, the LSM hooks can report whether a full file has been
read or not so that the contents can be reasoned about.

Signed-off-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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fs/kernel_read_file: Add file_size output argument

In preparation for adding partial read support, add an optional output
argument to kernel_read_file*() that reports the file size so callers
can re

fs/kernel_read_file: Add file_size output argument

In preparation for adding partial read support, add an optional output
argument to kernel_read_file*() that reports the file size so callers
can reason more easily about their reading progress.

Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Mimi Zohar <[email protected]>
Reviewed-by: Luis Chamberlain <[email protected]>
Reviewed-by: James Morris <[email protected]>
Acked-by: Scott Branden <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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fs/kernel_read_file: Switch buffer size arg to size_t

In preparation for further refactoring of kernel_read_file*(), rename
the "max_size" argument to the more accurate "buf_size", and correct
its t

fs/kernel_read_file: Switch buffer size arg to size_t

In preparation for further refactoring of kernel_read_file*(), rename
the "max_size" argument to the more accurate "buf_size", and correct
its type to size_t. Add kerndoc to explain the specifics of how the
arguments will be used. Note that with buf_size now size_t, it can no
longer be negative (and was never called with a negative value). Adjust
callers to use it as a "maximum size" when *buf is NULL.

Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Mimi Zohar <[email protected]>
Reviewed-by: Luis Chamberlain <[email protected]>
Reviewed-by: James Morris <[email protected]>
Acked-by: Scott Branden <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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fs/kernel_read_file: Remove redundant size argument

In preparation for refactoring kernel_read_file*(), remove the redundant
"size" argument which is not needed: it can be included in the return
cod

fs/kernel_read_file: Remove redundant size argument

In preparation for refactoring kernel_read_file*(), remove the redundant
"size" argument which is not needed: it can be included in the return
code, with callers adjusted. (VFS reads already cannot be larger than
INT_MAX.)

Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Mimi Zohar <[email protected]>
Reviewed-by: Luis Chamberlain <[email protected]>
Reviewed-by: James Morris <[email protected]>
Acked-by: Scott Branden <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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fs/kernel_read_file: Split into separate include file

Move kernel_read_file* out of linux/fs.h to its own linux/kernel_read_file.h
include file. That header gets pulled in just about everywhere
and

fs/kernel_read_file: Split into separate include file

Move kernel_read_file* out of linux/fs.h to its own linux/kernel_read_file.h
include file. That header gets pulled in just about everywhere
and doesn't really need functions not related to the general fs interface.

Suggested-by: Christoph Hellwig <[email protected]>
Signed-off-by: Scott Branden <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Mimi Zohar <[email protected]>
Reviewed-by: Luis Chamberlain <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Acked-by: James Morris <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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