From 2039bda1fa8dad3f4275b29eeaffef545bcbc85d Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 2 Oct 2020 10:38:23 -0700 Subject: LSM: Add "contents" flag to kernel_read_file hook 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 Reviewed-by: Mimi Zohar Link: https://lore.kernel.org/r/20201002173828.2099543-12-keescook@chromium.org Signed-off-by: Greg Kroah-Hartman --- security/loadpin/loadpin.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'security/loadpin/loadpin.c') diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c index 28782412febb..b12f7d986b1e 100644 --- a/security/loadpin/loadpin.c +++ b/security/loadpin/loadpin.c @@ -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 = { -- cgit v1.2.3