Since seccomp transitions between threads requires updates to the
no_new_privs flag to be atomic, the flag must be part of an atomic flag
set. This moves the nnp flag into a separate task field, and introduces
accessors.
Signed-off-by: Kees Cook <keesc...@chromium.org>
Reviewed-by: Oleg Nesterov <o...@redhat.com>
Reviewed-by: Andy Lutomirski <l...@amacapital.net>
---
fs/exec.c | 4 ++--
include/linux/sched.h | 18 +++++++++++++++---
kernel/seccomp.c | 2 +-
kernel/sys.c | 4 ++--
security/apparmor/domain.c | 4 ++--
5 files changed, 22 insertions(+), 10 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index a3d33fe592d6..0f5c272410f6 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1234,7 +1234,7 @@ static void check_unsafe_exec(struct linux_binprm *bprm)
* This isn't strictly necessary, but it makes it harder for LSMs to
* mess up.
*/
- if (current->no_new_privs)
+ if (task_no_new_privs(current))
bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
t = p;
@@ -1272,7 +1272,7 @@ int prepare_binprm(struct linux_binprm *bprm)
bprm->cred->egid = current_egid();
if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) &&
- !current->no_new_privs &&
+ !task_no_new_privs(current) &&
kuid_has_mapping(bprm->cred->user_ns, inode->i_uid) &&
kgid_has_mapping(bprm->cred->user_ns, inode->i_gid)) {
/* Set-uid? */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0376b054a0d0..45cec6b70eaf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1307,13 +1307,12 @@ struct task_struct {
* execve */
unsigned in_iowait:1;
- /* task may not gain privileges */
- unsigned no_new_privs:1;
-
/* Revert to default priority/policy when forking */
unsigned sched_reset_on_fork:1;
unsigned sched_contributes_to_load:1;
+ unsigned long atomic_flags; /* Flags needing atomic access. */
+
pid_t pid;
pid_t tgid;
@@ -1967,6 +1966,19 @@ static inline void memalloc_noio_restore(unsigned int
flags)
current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
}
+/* Per-process atomic flags. */
+#define PFA_NO_NEW_PRIVS 0x00000001 /* May not gain new privileges. */
+
+static inline bool task_no_new_privs(struct task_struct *p)
+{
+ return test_bit(PFA_NO_NEW_PRIVS, &p->atomic_flags);
+}
+
+static inline void task_set_no_new_privs(struct task_struct *p)
+{
+ set_bit(PFA_NO_NEW_PRIVS, &p->atomic_flags);
+}
+
/*
* task->jobctl flags
*/
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index f0652578af75..d2596136b0d1 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -241,7 +241,7 @@ static long seccomp_attach_filter(struct sock_fprog *fprog)
* This avoids scenarios where unprivileged tasks can affect the
* behavior of privileged children.
*/
- if (!current->no_new_privs &&
+ if (!task_no_new_privs(current) &&
security_capable_noaudit(current_cred(), current_user_ns(),
CAP_SYS_ADMIN) != 0)
return -EACCES;
diff --git a/kernel/sys.c b/kernel/sys.c
index 66a751ebf9d9..ce8129192a26 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1990,12 +1990,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long,
arg2, unsigned long, arg3,
if (arg2 != 1 || arg3 || arg4 || arg5)
return -EINVAL;
- current->no_new_privs = 1;
+ task_set_no_new_privs(current);
break;
case PR_GET_NO_NEW_PRIVS:
if (arg2 || arg3 || arg4 || arg5)
return -EINVAL;
- return current->no_new_privs ? 1 : 0;
+ return task_no_new_privs(current) ? 1 : 0;
case PR_GET_THP_DISABLE:
if (arg2 || arg3 || arg4 || arg5)
return -EINVAL;
diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index 452567d3a08e..d97cba3e3849 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -621,7 +621,7 @@ int aa_change_hat(const char *hats[], int count, u64 token,
bool permtest)
* There is no exception for unconfined as change_hat is not
* available.
*/
- if (current->no_new_privs)
+ if (task_no_new_privs(current))
return -EPERM;
/* released below */
@@ -776,7 +776,7 @@ int aa_change_profile(const char *ns_name, const char
*hname, bool onexec,
* no_new_privs is set because this aways results in a reduction
* of permissions.
*/
- if (current->no_new_privs && !unconfined(profile)) {
+ if (task_no_new_privs(current) && !unconfined(profile)) {
put_cred(cred);
return -EPERM;
}
--
1.7.9.5
--
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