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Date: Mon, 17 Jul 2017 13:43:15 +0300 From: Elena Reshetova <elena.reshetova@...el.com> To: linux-kernel@...r.kernel.org Cc: cgroups@...r.kernel.org, linux-audit@...hat.com, linux-fsdevel@...r.kernel.org, peterz@...radead.org, gregkh@...uxfoundation.org, viro@...iv.linux.org.uk, tj@...nel.org, mingo@...hat.com, hannes@...xchg.org, lizefan@...wei.com, acme@...nel.org, alexander.shishkin@...ux.intel.com, eparis@...hat.com, akpm@...ux-foundation.org, arnd@...db.de, luto@...nel.org, keescook@...omium.org, tglx@...utronix.de, Elena Reshetova <elena.reshetova@...el.com> Subject: [PATCH 04/15] kernel: convert task_struct.usage from atomic_t to refcount_t refcount_t type and corresponding API should be used instead of atomic_t when the variable is used as a reference counter. This allows to avoid accidental refcounter overflows that might lead to use-after-free situations. Suggested-by: Kees Cook <keescook@...omium.org> Reviewed-by: David Windsor <dwindsor@...il.com> Reviewed-by: Hans Liljestrand <ishkamiel@...il.com> Signed-off-by: Elena Reshetova <elena.reshetova@...el.com> --- include/linux/init_task.h | 2 +- include/linux/sched.h | 3 ++- include/linux/sched/task.h | 4 ++-- kernel/fork.c | 4 ++-- 4 files changed, 7 insertions(+), 6 deletions(-) diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 61777d6..7ba3fca 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -234,7 +234,7 @@ extern struct cred init_cred; INIT_TASK_TI(tsk) \ .state = 0, \ .stack = init_stack, \ - .usage = ATOMIC_INIT(2), \ + .usage = REFCOUNT_INIT(2), \ .flags = PF_KTHREAD, \ .prio = MAX_PRIO-20, \ .static_prio = MAX_PRIO-20, \ diff --git a/include/linux/sched.h b/include/linux/sched.h index 8337e2d..9380e44 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -20,6 +20,7 @@ #include <linux/seccomp.h> #include <linux/nodemask.h> #include <linux/rcupdate.h> +#include <linux/refcount.h> #include <linux/resource.h> #include <linux/latencytop.h> #include <linux/sched/prio.h> @@ -534,7 +535,7 @@ struct task_struct { randomized_struct_fields_start void *stack; - atomic_t usage; + refcount_t usage; /* Per task flags (PF_*), defined further below: */ unsigned int flags; unsigned int ptrace; diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index c97e5f0..afd5e58 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -86,13 +86,13 @@ extern void sched_exec(void); #define sched_exec() {} #endif -#define get_task_struct(tsk) do { atomic_inc(&(tsk)->usage); } while(0) +#define get_task_struct(tsk) do { refcount_inc(&(tsk)->usage); } while(0) extern void __put_task_struct(struct task_struct *t); static inline void put_task_struct(struct task_struct *t) { - if (atomic_dec_and_test(&t->usage)) + if (refcount_dec_and_test(&t->usage)) __put_task_struct(t); } diff --git a/kernel/fork.c b/kernel/fork.c index 337904a..cfd8a42 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -406,7 +406,7 @@ static inline void put_signal_struct(struct signal_struct *sig) void __put_task_struct(struct task_struct *tsk) { WARN_ON(!tsk->exit_state); - WARN_ON(atomic_read(&tsk->usage)); + WARN_ON(refcount_read(&tsk->usage)); WARN_ON(tsk == current); cgroup_free(tsk); @@ -561,7 +561,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) * One for us, one for whoever does the "release_task()" (usually * parent) */ - atomic_set(&tsk->usage, 2); + refcount_set(&tsk->usage, 2); #ifdef CONFIG_BLK_DEV_IO_TRACE tsk->btrace_seq = 0; #endif -- 2.7.4
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