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LSM: Add "contents" flag to kernel_read_file hook

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As with the kernel_load_data LSM hook, add a "contents" flag to the
kernel_read_file LSM hook that indicates whether the LSM can expect
a matching call to the kernel_post_read_file LSM hook with the full
contents of the file. With the coming addition of partial file read
support for kernel_read_file*() API, the LSM will no longer be able
to always see the entire contents of a file during the read calls.

For cases where the LSM must read examine the complete file contents,
it will need to do so on its own every time the kernel_read_file
hook is called with contents=false (or reject such cases). Adjust all
existing LSMs to retain existing behavior.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Link: https://lore.kernel.org/r/20201002173828.2099543-12-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kees Cook
2020-10-02 10:38:23 -07:00
committed by Greg Kroah-Hartman
parent 38f901735a
commit 2039bda1fa
9 changed files with 41 additions and 14 deletions
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security/loadpin/loadpin.c
+12 -2
View File
@@ -118,11 +118,21 @@ static void loadpin_sb_free_security(struct super_block *mnt_sb)
}
}
static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
static int loadpin_read_file(struct file *file, enum kernel_read_file_id id,
bool contents)
{
struct super_block *load_root;
const char *origin = kernel_read_file_id_str(id);
/*
* If we will not know that we'll be seeing the full contents
* then we cannot trust a load will be complete and unchanged
* off disk. Treat all contents=false hooks as if there were
* no associated file struct.
*/
if (!contents)
file = NULL;
/* If the file id is excluded, ignore the pinning. */
if ((unsigned int)id < ARRAY_SIZE(ignore_read_file_id) &&
ignore_read_file_id[id]) {
@@ -179,7 +189,7 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
static int loadpin_load_data(enum kernel_load_data_id id, bool contents)
{
return loadpin_read_file(NULL, (enum kernel_read_file_id) id);
return loadpin_read_file(NULL, (enum kernel_read_file_id) id, contents);
}
static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {