creds: restore -- Honor rst_mem_alloc rules

rst_mem_alloc rules might move previously allocated
blocks which means we can't reuse previously allocated
pointer if new block is created. Thus remember pointers
positions where needed and adjust them accordingly.

https://github.com/xemul/criu/issues/97Reported-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -2807,7 +2807,7 @@ static void rst_reloc_creds(struct thread_restore_args *thread_args,
 }
 
 static struct thread_creds_args *
-rst_prep_creds_args(struct thread_creds_args *prev, CredsEntry *ce)
+rst_prep_creds_args(CredsEntry *ce, unsigned long *prev_pos)
 {
 	unsigned long this_pos = rst_mem_cpos(RM_PRIVATE);
 	struct thread_creds_args *args;
@@ -2839,18 +2839,21 @@ rst_prep_creds_args(struct thread_creds_args *prev, CredsEntry *ce)
 
 		if (profile) {
 			size_t lsm_profile_len;
+			char *lsm_profile;
 
 			if (render_lsm_profile(profile, &rendered))
 				return ERR_PTR(-EINVAL);
 
 			args->mem_lsm_profile_pos = rst_mem_cpos(RM_PRIVATE);
 			lsm_profile_len = strlen(rendered);
-			args->lsm_profile = rst_mem_alloc(lsm_profile_len + 1, RM_PRIVATE);
-			if (!args->lsm_profile) {
+			lsm_profile = rst_mem_alloc(lsm_profile_len + 1, RM_PRIVATE);
+			if (!lsm_profile) {
 				xfree(rendered);
 				return ERR_PTR(-ENOMEM);
 			}
 
+			args = rst_mem_remap_ptr(this_pos, RM_PRIVATE);
+			args->lsm_profile = lsm_profile;
 			strncpy(args->lsm_profile, rendered, lsm_profile_len);
 			xfree(rendered);
 		}
@@ -2875,10 +2878,14 @@ rst_prep_creds_args(struct thread_creds_args *prev, CredsEntry *ce)
 	memcpy(args->cap_bnd, ce->cap_bnd, sizeof(args->cap_bnd));
 
 	if (ce->n_groups) {
+		unsigned int *groups;
+
 		args->mem_groups_pos = rst_mem_cpos(RM_PRIVATE);
-		args->groups = rst_mem_alloc(ce->n_groups * sizeof(u32), RM_PRIVATE);
-		if (!args->groups)
+		groups = rst_mem_alloc(ce->n_groups * sizeof(u32), RM_PRIVATE);
+		if (!groups)
 			return ERR_PTR(-ENOMEM);
+		args = rst_mem_remap_ptr(this_pos, RM_PRIVATE);
+		args->groups = groups;
 		memcpy(args->groups, ce->groups, ce->n_groups * sizeof(u32));
 	} else {
 		args->groups = NULL;
@@ -2887,8 +2894,15 @@ rst_prep_creds_args(struct thread_creds_args *prev, CredsEntry *ce)
 
 	args->mem_pos_next = 0;
 
-	if (prev)
-		prev->mem_pos_next = this_pos;
+	if (prev_pos) {
+		if (*prev_pos) {
+			struct thread_creds_args *prev;
+
+			prev = rst_mem_remap_ptr(*prev_pos, RM_PRIVATE);
+			prev->mem_pos_next = this_pos;
+		}
+		*prev_pos = this_pos;
+	}
 	return args;
 }
 
@@ -2908,7 +2922,7 @@ static int rst_prep_creds_from_img(pid_t pid)
 	if (ret > 0) {
 		struct thread_creds_args *args;
 
-		args = rst_prep_creds_args(NULL, ce);
+		args = rst_prep_creds_args(ce, NULL);
 		if (IS_ERR(args))
 			ret = PTR_ERR(args);
 		else
@@ -2921,6 +2935,7 @@ static int rst_prep_creds_from_img(pid_t pid)
 static int rst_prep_creds(pid_t pid, CoreEntry *core, unsigned long *creds_pos)
 {
 	struct thread_creds_args *args = NULL;
+	unsigned long this_pos = 0;
 	size_t i;
 
 	/*
@@ -2946,7 +2961,7 @@ static int rst_prep_creds(pid_t pid, CoreEntry *core, unsigned long *creds_pos)
 	for (i = 0; i < current->nr_threads; i++) {
 		CredsEntry *ce = current->core[i]->thread_core->creds;
 
-		args = rst_prep_creds_args(args, ce);
+		args = rst_prep_creds_args(ce, &this_pos);
 		if (IS_ERR(args))
 			return PTR_ERR(args);
 	}