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authorPhilippe Mikoyan <philippe.mikoyan@skat.systems>2018-02-07 02:40:49 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-02-07 05:32:46 +0300
commit87ad4b0d853e8a65d6002f4e7bd3dce4ae3a52da (patch)
treec1e7faec69a13a77606fd6e8c9578080ffe531e1 /ipc
parentbac7a1fff7926fb9891a18fe33650884b0e13e41 (diff)
downloadlinux-87ad4b0d853e8a65d6002f4e7bd3dce4ae3a52da.tar.xz
ipc: fix ipc data structures inconsistency
As described in the title, this patch fixes <ipc>id_ds inconsistency when <ipc>ctl_stat executes concurrently with some ds-changing function, e.g. shmat, msgsnd or whatever. For instance, if shmctl(IPC_STAT) is running concurrently with shmat, following data structure can be returned: {... shm_lpid = 0, shm_nattch = 1, ...} Link: http://lkml.kernel.org/r/20171202153456.6514-1-philippe.mikoyan@skat.systems Signed-off-by: Philippe Mikoyan <philippe.mikoyan@skat.systems> Reviewed-by: Davidlohr Bueso <dbueso@suse.de> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
-rw-r--r--ipc/msg.c20
-rw-r--r--ipc/sem.c10
-rw-r--r--ipc/shm.c20
-rw-r--r--ipc/util.c5
4 files changed, 43 insertions, 12 deletions
diff --git a/ipc/msg.c b/ipc/msg.c
index 1bbc029d2b17..0dcc6699dc53 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -476,9 +476,9 @@ static int msgctl_info(struct ipc_namespace *ns, int msqid,
static int msgctl_stat(struct ipc_namespace *ns, int msqid,
int cmd, struct msqid64_ds *p)
{
- int err;
struct msg_queue *msq;
- int success_return;
+ int id = 0;
+ int err;
memset(p, 0, sizeof(*p));
@@ -489,14 +489,13 @@ static int msgctl_stat(struct ipc_namespace *ns, int msqid,
err = PTR_ERR(msq);
goto out_unlock;
}
- success_return = msq->q_perm.id;
+ id = msq->q_perm.id;
} else {
msq = msq_obtain_object_check(ns, msqid);
if (IS_ERR(msq)) {
err = PTR_ERR(msq);
goto out_unlock;
}
- success_return = 0;
}
err = -EACCES;
@@ -507,6 +506,14 @@ static int msgctl_stat(struct ipc_namespace *ns, int msqid,
if (err)
goto out_unlock;
+ ipc_lock_object(&msq->q_perm);
+
+ if (!ipc_valid_object(&msq->q_perm)) {
+ ipc_unlock_object(&msq->q_perm);
+ err = -EIDRM;
+ goto out_unlock;
+ }
+
kernel_to_ipc64_perm(&msq->q_perm, &p->msg_perm);
p->msg_stime = msq->q_stime;
p->msg_rtime = msq->q_rtime;
@@ -516,9 +523,10 @@ static int msgctl_stat(struct ipc_namespace *ns, int msqid,
p->msg_qbytes = msq->q_qbytes;
p->msg_lspid = msq->q_lspid;
p->msg_lrpid = msq->q_lrpid;
- rcu_read_unlock();
- return success_return;
+ ipc_unlock_object(&msq->q_perm);
+ rcu_read_unlock();
+ return id;
out_unlock:
rcu_read_unlock();
diff --git a/ipc/sem.c b/ipc/sem.c
index 87bd38f38dc3..a4af04979fd2 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1213,10 +1213,20 @@ static int semctl_stat(struct ipc_namespace *ns, int semid,
if (err)
goto out_unlock;
+ ipc_lock_object(&sma->sem_perm);
+
+ if (!ipc_valid_object(&sma->sem_perm)) {
+ ipc_unlock_object(&sma->sem_perm);
+ err = -EIDRM;
+ goto out_unlock;
+ }
+
kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm);
semid64->sem_otime = get_semotime(sma);
semid64->sem_ctime = sma->sem_ctime;
semid64->sem_nsems = sma->sem_nsems;
+
+ ipc_unlock_object(&sma->sem_perm);
rcu_read_unlock();
return id;
diff --git a/ipc/shm.c b/ipc/shm.c
index 7acda23430aa..4643865e9171 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -909,9 +909,11 @@ static int shmctl_stat(struct ipc_namespace *ns, int shmid,
int cmd, struct shmid64_ds *tbuf)
{
struct shmid_kernel *shp;
- int result;
+ int id = 0;
int err;
+ memset(tbuf, 0, sizeof(*tbuf));
+
rcu_read_lock();
if (cmd == SHM_STAT) {
shp = shm_obtain_object(ns, shmid);
@@ -919,14 +921,13 @@ static int shmctl_stat(struct ipc_namespace *ns, int shmid,
err = PTR_ERR(shp);
goto out_unlock;
}
- result = shp->shm_perm.id;
+ id = shp->shm_perm.id;
} else {
shp = shm_obtain_object_check(ns, shmid);
if (IS_ERR(shp)) {
err = PTR_ERR(shp);
goto out_unlock;
}
- result = 0;
}
err = -EACCES;
@@ -937,7 +938,14 @@ static int shmctl_stat(struct ipc_namespace *ns, int shmid,
if (err)
goto out_unlock;
- memset(tbuf, 0, sizeof(*tbuf));
+ ipc_lock_object(&shp->shm_perm);
+
+ if (!ipc_valid_object(&shp->shm_perm)) {
+ ipc_unlock_object(&shp->shm_perm);
+ err = -EIDRM;
+ goto out_unlock;
+ }
+
kernel_to_ipc64_perm(&shp->shm_perm, &tbuf->shm_perm);
tbuf->shm_segsz = shp->shm_segsz;
tbuf->shm_atime = shp->shm_atim;
@@ -946,8 +954,10 @@ static int shmctl_stat(struct ipc_namespace *ns, int shmid,
tbuf->shm_cpid = shp->shm_cprid;
tbuf->shm_lpid = shp->shm_lprid;
tbuf->shm_nattch = shp->shm_nattch;
+
+ ipc_unlock_object(&shp->shm_perm);
rcu_read_unlock();
- return result;
+ return id;
out_unlock:
rcu_read_unlock();
diff --git a/ipc/util.c b/ipc/util.c
index ff045fec8d83..4ed5a17dd06f 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -23,9 +23,12 @@
* tree.
* - perform initial checks (capabilities, auditing and permission,
* etc).
- * - perform read-only operations, such as STAT, INFO commands.
+ * - perform read-only operations, such as INFO command, that
+ * do not demand atomicity
* acquire the ipc lock (kern_ipc_perm.lock) through
* ipc_lock_object()
+ * - perform read-only operations that demand atomicity,
+ * such as STAT command.
* - perform data updates, such as SET, RMID commands and
* mechanism-specific operations (semop/semtimedop,
* msgsnd/msgrcv, shmat/shmdt).