shm: handle separate PID namespaces case
shm_try_destroy_orphaned() and shm_try_destroy_current() didn't handle
the case of separate PID namespaces, but a single IPC namespace. If
there are tasks with the same PID values using the same shmem object,
the wrong destroy decision could be reached.
On shm segment creation store the pointer to the creator task in
shmid_kernel->shm_creator field and zero it on task exit. Then
use the ->shm_creator insread of shm_cprid in both functions. As
shmid_kernel object is already locked at this stage, no additional
locking is needed.
Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/ipc/shm.c b/ipc/shm.c
index 3f5b143..fdaf8be 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -239,7 +239,23 @@
if (IS_ERR(shp))
return 0;
- if (shp->shm_cprid != task_tgid_vnr(current)) {
+ if (shp->shm_creator != current) {
+ shm_unlock(shp);
+ return 0;
+ }
+
+ /*
+ * Mark it as orphaned to destroy the segment when
+ * kernel.shm_rmid_forced is changed.
+ * It is noop if the following shm_may_destroy() returns true.
+ */
+ shp->shm_creator = NULL;
+
+ /*
+ * Don't even try to destroy it. If shm_rmid_forced=0 and IPC_RMID
+ * is not set, it shouldn't be deleted here.
+ */
+ if (!ns->shm_rmid_forced) {
shm_unlock(shp);
return 0;
}
@@ -255,7 +271,6 @@
{
struct ipc_namespace *ns = data;
struct shmid_kernel *shp = shm_lock(ns, id);
- struct task_struct *task;
if (IS_ERR(shp))
return 0;
@@ -263,11 +278,8 @@
/*
* We want to destroy segments without users and with already
* exit'ed originating process.
- *
- * XXX: the originating process may exist in another pid namespace.
*/
- task = find_task_by_vpid(shp->shm_cprid);
- if (task != NULL) {
+ if (shp->shm_creator != NULL) {
shm_unlock(shp);
return 0;
}
@@ -295,7 +307,7 @@
if (!nsp)
return;
ns = nsp->ipc_ns;
- if (!ns || !ns->shm_rmid_forced)
+ if (!ns)
return;
/* Destroy all already created segments, but not mapped yet */
@@ -494,6 +506,7 @@
shp->shm_segsz = size;
shp->shm_nattch = 0;
shp->shm_file = file;
+ shp->shm_creator = current;
/*
* shmid gets reported as "inode#" in /proc/pid/maps.
* proc-ps tools use this. Changing this will break them.