In order for LSMs and IMA-appraisal to differentiate between the original
and new syscalls (eg. kexec, kernel modules, firmware), both the original
and new syscalls must call an LSM hook.
Commit 2e72d51b4ac3 ("security: introduce kernel_module_from_file hook")
introduced calling security_kernel_module_from_file() in both the original
and new syscalls. Commit a1db74209483 ("module: replace
copy_module_from_fd with kernel version") replaced these LSM calls with
security_kernel_read_file().
Commit e40ba6d56b41 ("firmware: replace call to fw_read_file_contents()
with kernel version") and commit b804defe4297 ("kexec: replace call to
copy_file_from_fd() with kernel version") replaced their own version of
reading a file from the kernel with the generic
kernel_read_file_from_path/fd() versions, which call the pre and post
security_kernel_read_file LSM hooks.
Missing are LSM calls in the original kexec syscall and firmware sysfs
fallback method. From a technical perspective there is no justification
for defining a new LSM hook, as the existing security_kernel_read_file()
works just fine. The original syscalls, however, do not read a file, so
the security hook name is inappropriate. Instead of defining a new LSM
hook, this patch defines security_kernel_read_blob() as a wrapper for
the existing LSM security_kernel_file_read() hook.
Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Changelog v2:
- Define a generic wrapper named security_kernel_read_blob() for
security_kernel_read_file().
Changelog v1:
- Define and call security_kexec_load(), a wrapper for
security_kernel_read_file().
---
include/linux/security.h | 6 ++++++
security/security.c | 6 ++++++
2 files changed, 12 insertions(+)
diff --git a/include/linux/security.h b/include/linux/security.h
index 63030c85ee19..4db1967a688b 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -323,6 +323,7 @@ int security_kernel_module_request(char *kmod_name);
int security_kernel_read_file(struct file *file, enum kernel_read_file_id id);
int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
enum kernel_read_file_id id);
+int security_kernel_read_blob(enum kernel_read_file_id id);
int security_task_fix_setuid(struct cred *new, const struct cred *old,
int flags);
int security_task_setpgid(struct task_struct *p, pid_t pgid);
@@ -922,6 +923,11 @@ static inline int security_kernel_post_read_file(struct file *file,
return 0;
}
+static inline int security_kernel_read_blob(enum kernel_read_file_id id)
+{
+ return 0;
+}
+
static inline int security_task_fix_setuid(struct cred *new,
const struct cred *old,
int flags)
diff --git a/security/security.c b/security/security.c
index 68f46d849abe..8f199b2bf4a2 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1044,6 +1044,12 @@ int security_kernel_read_file(struct file *file, enum kernel_read_file_id id)
}
EXPORT_SYMBOL_GPL(security_kernel_read_file);
+int security_kernel_read_blob(enum kernel_read_file_id id)
+{
+ return security_kernel_read_file(NULL, id);
+}
+EXPORT_SYMBOL_GPL(security_kernel_read_blob);
+
int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
enum kernel_read_file_id id)
{
--
2.7.5
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