mm: mark a vma as stack, if a value of sp is in it

/proc/PID/maps can contains not up to date information about a stack vma.
A kernel marks a VMA as stack, if thread_struct->usersp is in it,
but usersp is updated, when a process calls a syscall.

This problem is occured, when we try to dump/restore a process in a loop.
When a restorer resumes a process, a restorer vma will be marked as stack.

A thread stack should not be marked as stack, because its vma is mapped
w/o MAP_GROWSDOWN.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-dump.c

@@ -833,7 +833,8 @@ err:
 
 static int dump_task_core_all(pid_t pid, const struct proc_pid_stat *stat,
 		const struct parasite_dump_misc *misc, const struct parasite_ctl *ctl,
-		const struct cr_fdset *cr_fdset)
+		const struct cr_fdset *cr_fdset,
+		struct list_head *vma_area_list)
 {
 	int fd_core = fdset_fd(cr_fdset, CR_FD_CORE);
 	CoreEntry *core;
@@ -859,6 +860,8 @@ static int dump_task_core_all(pid_t pid, const struct proc_pid_stat *stat,
 	if (ret)
 		goto err_free;
 
+	mark_stack_vma(core->thread_info->gpregs->sp, vma_area_list);
+
 	ret = get_task_futex_robust_list(pid, core->thread_core);
 	if (ret)
 		goto err_free;
@@ -1423,7 +1426,8 @@ static int dump_one_task(struct pstree_item *item)
 		goto err_cure;
 	}
 
-	ret = dump_task_core_all(pid, &pps_buf, &misc, parasite_ctl, cr_fdset);
+	ret = dump_task_core_all(pid, &pps_buf, &misc,
+					parasite_ctl, cr_fdset, &vma_area_list);
 	if (ret) {
 		pr_err("Dump core (pid: %d) failed with %d\n", pid, ret);
 		goto err_cure;

cr-restore.c

@@ -1208,6 +1208,9 @@ static int sigreturn_restore(pid_t pid, CoreEntry *core, struct list_head *tgt_v
 	if (ret < 0)
 		goto err;
 
+	/* required to unmap stack _with_ guard page */
+	mark_stack_vma((long) &self_vma_list, &self_vma_list);
+
 	self_vmas_len = round_up((ret + 1) * sizeof(VmaEntry), PAGE_SIZE);
 	vmas_len = round_up((nr_vmas + 1) * sizeof(VmaEntry), PAGE_SIZE);
 

include/util.h

@@ -165,6 +165,8 @@ extern void pr_vma(unsigned int loglevel, const struct vma_area *vma_area);
 		p__;						\
 	})
 
+extern void mark_stack_vma(unsigned long sp, struct list_head *vma_area_list);
+
 extern int move_img_fd(int *img_fd, int want_fd);
 extern int close_safe(int *fd);
 

proc_parse.c

@@ -144,10 +144,7 @@ int parse_smaps(pid_t pid, struct list_head *vma_area_list, bool use_map_files)
 			goto err;
 		}
 
-		if (strstr(buf, "[stack")) {
-			vma_area->vma.status |= VMA_AREA_REGULAR | VMA_AREA_STACK;
-			vma_area->vma.flags  |= MAP_GROWSDOWN;
-		} else if (strstr(buf, "[vsyscall]")) {
+		if (strstr(buf, "[vsyscall]")) {
 			vma_area->vma.status |= VMA_AREA_VSYSCALL;
 		} else if (strstr(buf, "[vdso]")) {
 			vma_area->vma.status |= VMA_AREA_REGULAR | VMA_AREA_VDSO;

util.c

@@ -36,6 +36,20 @@
 
 #include "crtools.h"
 
+/* /proc/PID/maps can contain not up to date information about stack */
+void mark_stack_vma(unsigned long sp, struct list_head *vma_area_list)
+{
+	struct vma_area *vma_area;
+	list_for_each_entry(vma_area, vma_area_list, list) {
+		if (in_vma_area(vma_area, sp)) {
+			vma_area->vma.status |= VMA_AREA_STACK;
+			vma_area->vma.flags  |= MAP_GROWSDOWN;
+			return;
+		}
+	}
+	BUG();
+}
+
 void pr_vma(unsigned int loglevel, const struct vma_area *vma_area)
 {
 	if (!vma_area)