From: Vasiliy Ulyanov <v.ulyanov@samsung.com>
Date: Wed, 26 Aug 2015 09:15:21 +0000 (+0300)
Subject: [FIX] Workaround to skip page faults from Preload
X-Git-Tag: submit/tizen_2.4/20150912.103527~23
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=2b54b37c9a190cb48477fd68a0e004efaf64b163;p=kernel%2Fswap-modules.git

[FIX] Workaround to skip page faults from Preload

Attempts to read userspace stuff from probe handlers (e.g. like we
do in Preload) may lead to crashes.

Change-Id: I00009bb9dc19ba003740d078b9a36dee2f75c3f5
Signed-off-by: Vyacheslav Cherkashin <v.cherkashin@samsung.com>
---

diff --git a/preload/preload_module.c b/preload/preload_module.c
index 547edf9..580c066 100644
--- a/preload/preload_module.c
+++ b/preload/preload_module.c
@@ -374,6 +374,7 @@ static inline int __msg_sanitization(char *user_msg, size_t len,
 static bool __is_proc_mmap_mappable(struct task_struct *task)
 {
 	struct vm_area_struct *linker_vma = __get_linker_vma(task);
+	struct sspt_proc *proc;
 	unsigned long r_debug_addr;
 	unsigned int state;
 	enum { r_state_offset = sizeof(int) + sizeof(void *) + sizeof(long) };
@@ -386,6 +387,10 @@ static bool __is_proc_mmap_mappable(struct task_struct *task)
 		return false;
 
 	r_debug_addr += r_state_offset;
+	proc = sspt_proc_get_by_task(task);
+	if (proc)
+		proc->r_state_addr = r_debug_addr;
+
 	if (get_user(state, (unsigned long *)r_debug_addr))
 		return false;
 
diff --git a/us_manager/helper.c b/us_manager/helper.c
index d71adf4..3ba5c4f 100644
--- a/us_manager/helper.c
+++ b/us_manager/helper.c
@@ -68,6 +68,14 @@ static int entry_handler_pf(struct kretprobe_instance *ri, struct pt_regs *regs)
 	#error "this architecture is not supported"
 #endif /* CONFIG_arch */
 
+	if (data->addr) {
+		struct sspt_proc * proc = sspt_proc_get_by_task(current);
+
+		if (proc && (proc->r_state_addr == data->addr))
+			/* skip ret_handler_pf() for current task */
+			return 1;
+	}
+
 	return 0;
 }
 
diff --git a/us_manager/sspt/sspt_proc.c b/us_manager/sspt/sspt_proc.c
index 01f0353..85d24f4 100644
--- a/us_manager/sspt/sspt_proc.c
+++ b/us_manager/sspt/sspt_proc.c
@@ -88,7 +88,7 @@ void sspt_proc_write_unlock(void)
  */
 struct sspt_proc *sspt_proc_create(struct task_struct *task)
 {
-	struct sspt_proc *proc = kmalloc(sizeof(*proc), GFP_ATOMIC);
+	struct sspt_proc *proc = kzalloc(sizeof(*proc), GFP_ATOMIC);
 
 	if (proc) {
 		proc->feature = sspt_create_feature();
@@ -101,8 +101,6 @@ struct sspt_proc *sspt_proc_create(struct task_struct *task)
 		proc->tgid = task->tgid;
 		proc->task = task->group_leader;
 		proc->sm = create_sm_us(task);
-		proc->first_install = 0;
-		proc->private_data = NULL;
 		INIT_LIST_HEAD(&proc->file_list);
 		INIT_LIST_HEAD(&proc->filter_list);
 		atomic_set(&proc->usage, 1);
diff --git a/us_manager/sspt/sspt_proc.h b/us_manager/sspt/sspt_proc.h
index 534f150..d82a271 100644
--- a/us_manager/sspt/sspt_proc.h
+++ b/us_manager/sspt/sspt_proc.h
@@ -48,6 +48,7 @@ struct sspt_proc {
 	struct list_head list;		/**< For global process list */
 	pid_t tgid;			/**< Thread group ID */
 	struct task_struct *task;	/**< Ptr to the task */
+	unsigned long r_state_addr;	/**< address of r_state */
 	struct slot_manager *sm;	/**< Ptr to the manager slot */
 	struct list_head file_list;	/**< For sspt_file */
 	struct list_head filter_list;	/**< Filter list */