Re: [PATCH] security: Add LSM hooks to set*gid syscalls
From: Kees Cook <hidden>
Date: 2020-06-05 21:25:54
On Fri, Jun 05, 2020 at 12:38:05PM -0700, Micah Morton wrote:
The SafeSetID LSM uses the security_task_fix_setuid hook to filter set*uid() syscalls according to its configured security policy. In preparation for adding analagous support in the LSM for set*gid() syscalls, we add the requisite hook here. Tested by putting print statements in the security_task_fix_setgid hook and seeing them get hit during kernel boot. From: Thomas Cedeno <redacted>
^^^ this line should be before the commit log body (many tools won't find it here).
quoted hunk ↗ jump to hunk
Signed-off-by: Thomas Cedeno <redacted> Reviewed-by: Micah Morton <mortonm@chromium.org> --- NOTE: I (Micah) will send this patch as a pull request to Linus through my SafeSetID tree if there are no objections. include/linux/lsm_hook_defs.h | 2 ++ include/linux/lsm_hooks.h | 9 +++++++++ include/linux/security.h | 9 +++++++++ kernel/sys.c | 15 ++++++++++++++- security/security.c | 6 ++++++ 5 files changed, 40 insertions(+), 1 deletion(-)diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index fb3ce6cec997..d5401c09f2d3 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h@@ -191,6 +191,8 @@ LSM_HOOK(int, 0, kernel_post_read_file, struct file *file, char *buf, loff_t size, enum kernel_read_file_id id) LSM_HOOK(int, 0, task_fix_setuid, struct cred *new, const struct cred *old, int flags) +LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old, + int flags) LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid) LSM_HOOK(int, 0, task_getpgid, struct task_struct *p) LSM_HOOK(int, 0, task_getsid, struct task_struct *p)diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 3e62dab77699..8012b610fe53 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h@@ -659,6 +659,15 @@ * @old is the set of credentials that are being replaces * @flags contains one of the LSM_SETID_* values. * Return 0 on success. + * @task_fix_setgid: + * Update the module's state after setting one or more of the group + * identity attributes of the current process. The @flags parameter + * indicates which of the set*gid system calls invoked this hook. + * @new is the set of credentials that will be installed. Modifications + * should be made to this rather than to @current->cred. + * @old is the set of credentials that are being replaced. + * @flags contains one of the LSM_SETID_* values. + * Return 0 on success.
The indenting here appears to be using spaces instead of a tab. Everything else looks okay. (There are a surprising number of gid changing places...) -- Kees Cook