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ipc: fix ipc data structures inconsistency

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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>
This commit is contained in:
Philippe Mikoyan 2018-02-06 15:40:49 -08:00 committed by Linus Torvalds
parent bac7a1fff7
commit 87ad4b0d85
4 changed files with 43 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
ipc/msg.c
View File

@ -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();

10
ipc/sem.c
View File

@ -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;

20
ipc/shm.c
View File

@ -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();

5
ipc/util.c
View File

@ -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).