From: Manfred Spraul <manfred@colorfullife.com>
My discussion with Ulrich had one result:
- mq_setattr can accept implementation defined flags. Right now we have
none, but we might add some later (e.g. switch to CLOCK_MONOTONIC for
mq_timed{send,receive} or something similar). When we add flags, we
might need the fields for additional information. And they don't hurt.
Therefore add four __reserved fields to mq_attr.
- fail mq_setattr if we get unknown flags - otherwise glibc can't detect
if it's running on a future kernel that supports new features.
- use memset to initialize the mq_attr structure - theoretically we could
leak kernel memory.
- Only set O_NONBLOCK in mq_attr, explicitely clear O_RDWR & friends.
openposix uses getattr, attr |=O_NONBLOCK, setattr - a sane approach.
Without clearing O_RDWR, this fails.
I've retested all openposix conformance tests with the new patch - the two
new FAILED tests check undefined behavior. Note that I won't have net
access until Sunday - if the message queue patch breaks something important
either ask Krzysztof or drop it.
Ulrich had another good idea for SIGEV_THREAD, but I must think about it.
It would mean less complexitiy in glibc, but more code in the kernel. I'm
not yet convinced that it's overall better.
---
25-akpm/include/linux/mqueue.h | 1 +
25-akpm/ipc/mqueue.c | 6 ++++--
2 files changed, 5 insertions(+), 2 deletions(-)
diff -puN include/linux/mqueue.h~mq-update-01 include/linux/mqueue.h
--- 25/include/linux/mqueue.h~mq-update-01 Wed Apr 7 12:12:46 2004
+++ 25-akpm/include/linux/mqueue.h Wed Apr 7 12:12:46 2004
@@ -27,6 +27,7 @@ struct mq_attr {
long mq_maxmsg; /* maximum number of messages */
long mq_msgsize; /* maximum message size */
long mq_curmsgs; /* number of messages currently queued */
+ long __reserved[4]; /* ignored for input, zeroed for output */
};
#define NOTIFY_NONE 0
diff -puN ipc/mqueue.c~mq-update-01 ipc/mqueue.c
--- 25/ipc/mqueue.c~mq-update-01 Wed Apr 7 12:12:46 2004
+++ 25-akpm/ipc/mqueue.c Wed Apr 7 12:12:46 2004
@@ -121,7 +121,7 @@ static struct inode *mqueue_get_inode(st
INIT_LIST_HEAD(&info->e_wait_q[1].list);
info->notify_owner = 0;
info->qsize = 0;
- info->attr.mq_curmsgs = 0;
+ memset(&info->attr, 0, sizeof(info->attr));
info->attr.mq_maxmsg = DFLT_MSGMAX;
info->attr.mq_msgsize = DFLT_MSGSIZEMAX;
info->messages = kmalloc(DFLT_MSGMAX * sizeof(struct msg_msg *), GFP_KERNEL);
@@ -1078,6 +1078,8 @@ asmlinkage long sys_mq_getsetattr(mqd_t
if (u_mqstat != NULL) {
if (copy_from_user(&mqstat, u_mqstat, sizeof(struct mq_attr)))
return -EFAULT;
+ if (mqstat.mq_flags & (~O_NONBLOCK))
+ return -EINVAL;
}
ret = -EBADF;
@@ -1093,7 +1095,7 @@ asmlinkage long sys_mq_getsetattr(mqd_t
spin_lock(&info->lock);
omqstat = info->attr;
- omqstat.mq_flags = filp->f_flags;
+ omqstat.mq_flags = filp->f_flags & O_NONBLOCK;
if (u_mqstat) {
if (mqstat.mq_flags & O_NONBLOCK)
filp->f_flags |= O_NONBLOCK;
_