[kernel-hardening] [PATCH v5 05/10] seccomp: Split put_seccomp_filter() with put_seccomp()

Mickaël Salaün
2017-02-22T01:26:27Z

The semantic is unchanged. This will be useful for the Landlock
integration with seccomp (next commit).

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
---
include/linux/seccomp.h | 4 ++--
kernel/fork.c | 2 +-
kernel/seccomp.c | 18 +++++++++++++-----
3 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index ecc296c137cd..e25aee2cdfc0 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -77,10 +77,10 @@ static inline int seccomp_mode(struct seccomp *s)
#endif /* CONFIG_SECCOMP */

#ifdef CONFIG_SECCOMP_FILTER
-extern void put_seccomp_filter(struct task_struct *tsk);
+extern void put_seccomp(struct task_struct *tsk);
extern void get_seccomp_filter(struct task_struct *tsk);
#else /* CONFIG_SECCOMP_FILTER */
-static inline void put_seccomp_filter(struct task_struct *tsk)
+static inline void put_seccomp(struct task_struct *tsk)
{
return;
}
diff --git a/kernel/fork.c b/kernel/fork.c
index 11c5c8ab827c..a4f0d0e8aeb2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -352,7 +352,7 @@ void free_task(struct task_struct *tsk)
#endif
rt_mutex_debug_task_free(tsk);
ftrace_graph_exit_task(tsk);
- put_seccomp_filter(tsk);
+ put_seccomp(tsk);
arch_release_task_struct(tsk);
if (tsk->flags & PF_KTHREAD)
free_kthread_struct(tsk);
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index f7ce79a46050..06f2f3ee454c 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -62,6 +62,8 @@ struct seccomp_filter {
/* Limit any path through the tree to 256KB worth of instructions. */
#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))

+static void put_seccomp_filter(struct seccomp_filter *filter);
+
/*
* Endianness is explicitly ignored and left for BPF program authors to manage
* as per the specific architecture.
@@ -312,7 +314,7 @@ static inline void seccomp_sync_threads(void)
* current's path will hold a reference. (This also
* allows a put before the assignment.)
*/
- put_seccomp_filter(thread);
+ put_seccomp_filter(thread->seccomp.filter);
smp_store_release(&thread->seccomp.filter,
caller->seccomp.filter);

@@ -474,10 +476,11 @@ static inline void seccomp_filter_free(struct seccomp_filter *filter)
}
}

-/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
-void put_seccomp_filter(struct task_struct *tsk)
+/* put_seccomp_filter - decrements the ref count of a filter */
+static void put_seccomp_filter(struct seccomp_filter *filter)
{
- struct seccomp_filter *orig = tsk->seccomp.filter;
+ struct seccomp_filter *orig = filter;
+
/* Clean up single-reference branches iteratively. */
while (orig && atomic_dec_and_test(&orig->usage)) {
struct seccomp_filter *freeme = orig;
@@ -486,6 +489,11 @@ void put_seccomp_filter(struct task_struct *tsk)
}
}

+void put_seccomp(struct task_struct *tsk)
+{
+ put_seccomp_filter(tsk->seccomp.filter);
+}
+
/**
* seccomp_send_sigsys - signals the task to allow in-process syscall emulation
* @syscall: syscall number to send to userland
@@ -897,7 +905,7 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
ret = -EFAULT;

- put_seccomp_filter(task);
+ put_seccomp_filter(task->seccomp.filter);
return ret;

out:
--
2.11.0