[CRIU] [PATCH] Take into account stack guard page size in parse_smaps

[Cyrill Gorcunov]

Otherwise we might not unmap the whole stack leaving
a guard page in restoree memory map. Not a big deal
but anyway.

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
---
 proc_parse.c |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/proc_parse.c b/proc_parse.c
index 0d80011..3c5c27c 100644
--- a/proc_parse.c
+++ b/proc_parse.c
@@ -146,6 +146,26 @@ int parse_smaps(pid_t pid, struct list_head *vma_area_list, bool use_map_files)
 		if (strstr(buf, "[stack")) {
 			vma_area->vma.status |= VMA_AREA_REGULAR | VMA_AREA_STACK;
 			vma_area->vma.flags  |= MAP_GROWSDOWN;
+
+			/*
+			 * For a moment we can't figure out if
+			 * stack is allocated with MAP_GROWSUP,
+			 * need to add some flag into a kernel.
+			 *
+			 * But still for stack the kernel hides guard
+			 * page so we add this page manually.
+			 *
+			 * For MAP_GROWSDOWN one page on bottom is hidden,
+			 * for MAP_GROWSUP the reverse -- one page on top.
+			 */
+
+			if (vma_area->vma.start < PAGE_SIZE) {
+				pr_err("Can't handle stack guard page on %d's map %lu\n",
+				       pid, vma_area->vma.start);
+				goto err;
+			}
+			vma_area->vma.start -= PAGE_SIZE;
+
 		} else if (strstr(buf, "[vsyscall]")) {
 			vma_area->vma.status |= VMA_AREA_VSYSCALL;
 		} else if (strstr(buf, "[vdso]")) {
-- 
1.7.7.6