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Date: Wed, 19 Apr 2017 00:47:54 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Kees Cook <keescook@...omium.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
Andy Lutomirski <luto@...capital.net>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Casey Schaufler <casey@...aufler-ca.com>,
Daniel Borkmann <daniel@...earbox.net>,
David Drysdale
<drysdale@...gle.com>,
"David S . Miller" <davem@...emloft.net>,
"Eric W . Biederman" <ebiederm@...ssion.com>,
James Morris <james.l.morris@...cle.com>, Jann Horn <jann@...jh.net>,
Jonathan Corbet <corbet@....net>,
Matthew Garrett <mjg59@...f.ucam.org>,
Michael Kerrisk <mtk.manpages@...il.com>,
Paul Moore <paul@...l-moore.com>, Sargun Dhillon <sargun@...gun.me>,
"Serge E . Hallyn" <serge@...lyn.com>, Shuah Khan <shuah@...nel.org>,
Tejun Heo <tj@...nel.org>, Thomas Graf <tgraf@...g.ch>,
Will Drewry <wad@...omium.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Linux API <linux-api@...r.kernel.org>,
linux-security-module <linux-security-module@...r.kernel.org>,
Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v6 05/11] seccomp: Split put_seccomp_filter()
with put_seccomp()
On 19/04/2017 00:23, Kees Cook wrote:
> On Tue, Mar 28, 2017 at 4:46 PM, Mickaël Salaün <mic@...ikod.net> wrote:
>> The semantic is unchanged. This will be useful for the Landlock
>> integration with seccomp (next commit).
>>
>> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
>> Cc: Kees Cook <keescook@...omium.org>
>> Cc: Andy Lutomirski <luto@...capital.net>
>> Cc: Will Drewry <wad@...omium.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 6c463c80e93d..a27d8e67ce33 100644
>> --- a/kernel/fork.c
>> +++ b/kernel/fork.c
>> @@ -363,7 +363,7 @@ 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 65f61077ad50..326f79e32127 100644
>> --- a/kernel/seccomp.c
>> +++ b/kernel/seccomp.c
>> @@ -64,6 +64,8 @@ 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);
>
> Can this be reorganized easily to avoid a forward-declaration?
I didn't want to move too much code but I will.
>
>> +
>> /*
>> * Endianness is explicitly ignored and left for BPF program authors to manage
>> * as per the specific architecture.
>> @@ -314,7 +316,7 @@ 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);
>>
>> @@ -476,10 +478,11 @@ 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;
>> @@ -488,6 +491,11 @@ void put_seccomp_filter(struct task_struct *tsk)
>> }
>> }
>>
>> +void put_seccomp(struct task_struct *tsk)
>> +{
>> + put_seccomp_filter(tsk->seccomp.filter);
>> +}
>> +
>> static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason)
>> {
>> memset(info, 0, sizeof(*info));
>> @@ -914,7 +922,7 @@ 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;
>
> I don't like that the arguments to get_seccomp_filter() and
> put_seccomp_filter() are now different. I think they should match for
> readability.
OK, I can do that.
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