On Tue, 2013-06-25 at 23:41 +0200, Sedat Dilek wrote:
> On Tue, Jun 25, 2013 at 10:33 PM, Davidlohr Bueso
> <davidlohr.bueso@xxxxxx> wrote:
> > On Tue, 2013-06-25 at 18:10 +0200, Sedat Dilek wrote:
> > [...]
> >
> >> I did some more testing with Linux-Testing-Project (release:
> >> ltp-full-20130503) and next-20130624 (Monday) which has still the
> >> issue, here.
> >>
> >> If I revert the mentioned two commits from my local
> >> revert-ipc-next20130624-5089fd1c6a6a-ab9efc2d0db5 GIT repo, everything
> >> is fine.
> >>
> >> I have tested the LTP ***IPC*** and ***SYSCALLS*** testcases.
> >>
> >> root# ./runltp -f ipc
> >>
> >> root# ./runltp -f syscalls
> >
> > These are nice test cases!
> >
> > So I was able to reproduce the issue with LTP and manually running
> > msgctl08. We seemed to be racing at find_msg(), so take to q_perm lock
> > before calling it. The following changes fixes the issue and passes all
> > 'runltp -f syscall' tests, could you give it a try?
> >
>
> Cool, that fixes the issues here.
>
> Building with fakeroot & make deb-pkg is now OK, again.
>
> The syscalls/msgctl08 test-case ran successfully!
Andrew, could you pick this one up? I've made the patch on top of
3.10.0-rc7-next-20130625
Thanks.
Davidlohr
8<---------------------------------
From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Subject: [PATCH] ipc,msq: fix race in msgrcv(2)
Sedat reported the following issue when building the latest linux-next:
Building via 'make deb-pkg' with fakeroot fails here like this:
make: *** [deb-pkg] Terminated
/usr/bin/fakeroot: line 181: 2386 Terminated
FAKEROOTKEY=$FAKEROOTKEY LD_LIBRARY_PATH="$PATHS" LD_PRELOAD="$LIB"
"$@"
semop(1): encountered an error: Identifier removed
semop(2): encountered an error: Invalid argument
semop(1): encountered an error: Identifier removed
semop(1): encountered an error: Identifier removed
semop(1): encountered an error: Invalid argument
semop(1): encountered an error: Invalid argument
semop(1): encountered an error: Invalid argument
The issue was caused by a race in find_msg(), so acquire the q_perm.lock
before calling the function. This also broke some LTP test cases:
<<<test_start>>>
tag=msgctl08 stime=1372174954
cmdline="msgctl08"
contacts=""
analysis=exit
<<<test_output>>>
msgctl08 0 TWARN : Verify error in child 0, *buf = 28, val = 27, size = 8
msgctl08 1 TFAIL : in child 0 read # = 73,key = 127
msgctl08 0 TWARN : Verify error in child 3, *buf = ffffff8a, val
= ffffff89, size = 52
msgctl08 1 TFAIL : in child 3 read # = 157,key = 189
msgctl08 0 TWARN : Verify error in child 2, *buf = ffffff87, val
= ffffff86, size = 71
msgctl08 1 TFAIL : in child 2 read # = 15954,key = 3e86
msgctl08 0 TWARN : Verify error in child 12, *buf = ffffffa9,
val = ffffffa8, size = 22
msgctl08 1 TFAIL : in child 12 read # = 12904,key = 32a8
msgctl08 0 TWARN : Verify error in child 13, *buf = 36, val =
35, size = 27
...
Also update a comment referring to ipc_lock_by_ptr(), which has already been deleted
and no longer applies to this context.
Reported-and-tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Signed-off-by: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
---
ipc/msg.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/ipc/msg.c b/ipc/msg.c
index a1cf70e..bd60d7e 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -895,6 +895,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
if (ipcperms(ns, &msq->q_perm, S_IRUGO))
goto out_unlock1;
+ ipc_lock_object(&msq->q_perm);
msg = find_msg(msq, &msgtyp, mode);
if (!IS_ERR(msg)) {
/*
@@ -903,7 +904,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
*/
if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
msg = ERR_PTR(-E2BIG);
- goto out_unlock1;
+ goto out_unlock0;
}
/*
* If we are copying, then do not unlink message and do
@@ -911,10 +912,9 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
*/
if (msgflg & MSG_COPY) {
msg = copy_msg(msg, copy);
- goto out_unlock1;
+ goto out_unlock0;
}
- ipc_lock_object(&msq->q_perm);
list_del(&msg->m_list);
msq->q_qnum--;
msq->q_rtime = get_seconds();
@@ -930,10 +930,9 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
/* No message waiting. Wait for a message */
if (msgflg & IPC_NOWAIT) {
msg = ERR_PTR(-ENOMSG);
- goto out_unlock1;
+ goto out_unlock0;
}
- ipc_lock_object(&msq->q_perm);
list_add_tail(&msr_d.r_list, &msq->q_receivers);
msr_d.r_tsk = current;
msr_d.r_msgtype = msgtyp;
@@ -957,7 +956,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
* Prior to destruction, expunge_all(-EIRDM) changes r_msg.
* Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
* rcu_read_lock() prevents preemption between reading r_msg
- * and the spin_lock() inside ipc_lock_by_ptr().
+ * and acquiring the q_perm.lock in ipc_lock_object().
*/
rcu_read_lock();
--
1.7.11.7
--
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