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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
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20
ipc/msg.c
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@@ -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();