Messages in this thread Patch in this message | | | Date | Wed, 20 Sep 2017 14:56:21 +0200 | From | Oleg Nesterov <> | Subject | [PATCH] seccomp: fix the usage of get/put_seccomp_filter() in seccomp_get_filter() |
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As Chris explains, get_seccomp_filter() and put_seccomp_filter() can use the different filters, once we drop ->siglock task->seccomp.filter can be replaced by SECCOMP_FILTER_FLAG_TSYNC.
Fixes: f8e529ed941b ("seccomp, ptrace: add support for dumping seccomp filters") Reported-by: Chris Salls <chrissalls5@gmail.com> Cc: stable@vger.kernel.org Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/seccomp.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 98b59b5..897f153 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -476,10 +476,8 @@ 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) +static void __put_seccomp_filter(struct seccomp_filter *orig) { - struct seccomp_filter *orig = tsk->seccomp.filter; /* Clean up single-reference branches iteratively. */ while (orig && refcount_dec_and_test(&orig->usage)) { struct seccomp_filter *freeme = orig; @@ -488,6 +486,12 @@ void put_seccomp_filter(struct task_struct *tsk) } } +/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */ +void put_seccomp_filter(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)); @@ -908,13 +912,13 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, if (!data) goto out; - get_seccomp_filter(task); + refcount_inc(&filter->usage); spin_unlock_irq(&task->sighand->siglock); if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) ret = -EFAULT; - put_seccomp_filter(task); + __put_seccomp_filter(filter); return ret; out: -- 2.5.0
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