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dump: Check for pids reuse at suspend

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While we try to seize task it can die and give its pid to
somebody else. This can break pstree consistency. Check for
parent being valid after task is seized.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
This commit is contained in:
Pavel Emelyanov
2012-03-01 19:04:31 +04:00
committed by Cyrill Gorcunov
parent f8a18edd44
commit 199e8d8248
6 changed files with 32 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
cr-dump.c
View File

@@ -848,7 +848,7 @@ static int seize_threads(struct pstree_item *item)
continue;
pr_info("\tSeizing %d's %d thread\n", item->pid, item->threads[i]);
ret = seize_task(item->threads[i]);
ret = seize_task(item->threads[i], item->ppid);
if (ret < 0)
goto err;
@@ -887,7 +887,7 @@ static int collect_threads(struct pstree_item *item)
return ret;
}
static struct pstree_item *collect_task(pid_t pid, struct list_head *list)
static struct pstree_item *collect_task(pid_t pid, pid_t ppid, struct list_head *list)
{
int ret;
struct pstree_item *item;
@@ -896,12 +896,13 @@ static struct pstree_item *collect_task(pid_t pid, struct list_head *list)
if (!item)
goto err;
ret = seize_task(pid);
ret = seize_task(pid, ppid);
if (ret < 0)
goto err_free;
pr_info("Seized task %d, state %d\n", pid, ret);
item->pid = pid;
item->ppid = ppid;
item->state = ret;
ret = collect_threads(item);
@@ -932,13 +933,14 @@ err:
return NULL;
}
static int collect_pstree(pid_t pid, struct list_head *pstree_list, int leader_only)
static int collect_subtree(pid_t pid, pid_t ppid, struct list_head *pstree_list,
int leader_only)
{
struct pstree_item *item;
int i;
pr_info("Collecting tasks starting from %d\n", pid);
item = collect_task(pid, pstree_list);
item = collect_task(pid, ppid, pstree_list);
if (item == NULL)
return -1;
@@ -946,12 +948,17 @@ static int collect_pstree(pid_t pid, struct list_head *pstree_list, int leader_o
return 0;
for (i = 0; i < item->nr_children; i++)
if (collect_pstree(item->children[i], pstree_list, 0) < 0)
if (collect_subtree(item->children[i], item->pid, pstree_list, 0) < 0)
return -1;
return 0;
}
static int collect_pstree(pid_t pid, struct list_head *pstree_list, int leader_only)
{
return collect_subtree(pid, -1, pstree_list, leader_only);
}
static int dump_pstree(pid_t pid, struct list_head *pstree_list, struct cr_fdset *cr_fdset)
{
struct pstree_item *item;

1
include/crtools.h
View File

@@ -150,6 +150,7 @@ struct vma_area {
struct pstree_item {
struct list_head list;
pid_t pid; /* leader pid */
pid_t ppid;
int state; /* TASK_XXX constants */
u32 nr_children; /* number of children */
u32 nr_threads; /* number of threads */

1
include/proc_parse.h
View File

@@ -8,6 +8,7 @@ struct proc_pid_stat_small {
int pid;
char comm[PROC_TASK_COMM_LEN];
char state;
int ppid;
};
struct proc_pid_stat {

2
include/ptrace.h
View File

@@ -32,7 +32,7 @@
#define PTRACE_O_TRACEVFORKDONE 0x00000020
#define PTRACE_O_TRACEEXIT 0x00000040
extern int seize_task(pid_t pid);
extern int seize_task(pid_t pid, pid_t ppid);
extern int unseize_task(pid_t pid, enum cr_task_state st);
extern int ptrace_peek_area(pid_t pid, void *dst, void *addr, long bytes);
extern int ptrace_poke_area(pid_t pid, void *src, void *addr, long bytes);

6
proc_parse.c
View File

@@ -190,10 +190,10 @@ int parse_pid_stat_small(pid_t pid, struct proc_pid_stat_small *s)
return -1;
memset(s, 0, sizeof(*s));
n = fscanf(f, "%d " PROC_TASK_COMM_LEN_FMT " %c",
&s->pid, s->comm, &s->state);
n = fscanf(f, "%d " PROC_TASK_COMM_LEN_FMT " %c %d",
&s->pid, s->comm, &s->state, &s->ppid);
if (n < 3) {
if (n < 4) {
pr_err("Parsing %d's stat failed (#fields do not match)\n", pid);
return -1;
}

21
ptrace.c
View File

@@ -40,21 +40,20 @@ int unseize_task(pid_t pid, enum cr_task_state st)
* up with someone else.
*/
int seize_task(pid_t pid)
int seize_task(pid_t pid, pid_t ppid)
{
siginfo_t si;
int status;
int ret;
int ret, ret2;
struct proc_pid_stat_small ps;
ret = ptrace(PTRACE_SEIZE, pid, NULL,
(void *)(unsigned long)PTRACE_SEIZE_DEVEL);
ret2 = parse_pid_stat_small(pid, &ps);
if (ret2 < 0)
return -1;
if (ret < 0) {
struct proc_pid_stat_small ps;
ret = parse_pid_stat_small(pid, &ps);
if (ret < 0)
return -1;
if (ps.state != 'Z') {
pr_err("Unseizeable non-zombie %d found, state %c\n",
pid, ps.state);
@@ -64,6 +63,12 @@ int seize_task(pid_t pid)
return TASK_DEAD;
}
if ((ppid != -1) && (ps.ppid != ppid)) {
pr_err("Task pid reused while suspending (%d: %d -> %d)\n",
pid, ppid, ps.ppid);
goto err;
}
ret = ptrace(PTRACE_INTERRUPT, pid, NULL, NULL);
if (ret < 0) {
pr_perror("SEIZE %d: can't interrupt task", pid);