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Message-ID: <50D5D50B.8090309@oracle.com> Date: Sat, 22 Dec 2012 10:43:07 -0500 From: Sasha Levin <sasha.levin@...cle.com> To: Stanislav Kinsbursky <skinsbursky@...allels.com> CC: Andrew Morton <akpm@...ux-foundation.org>, serge.hallyn@...onical.com, ebiederm@...ssion.com, linux-kernel@...r.kernel.org, xemul@...allels.com, catalin.marinas@....com, will.deacon@....com, jmorris@...ei.org, cmetcalf@...era.com, joe.korty@...r.com, dhowells@...hat.com, dledford@...hat.com, viro@...iv.linux.org.uk, kosaki.motohiro@...fujitsu.com, linux-api@...r.kernel.org, serue@...ibm.com, tglx@...utronix.de, paulmck@...ux.vnet.ibm.com, devel@...nvz.org, mtk.manpages@...il.com, Wu Fengguang <fengguang.wu@...el.com> Subject: Re: [RFC PATCH v8 0/5] IPC: checkpoint/restore in userspace enhancements On 12/21/2012 04:57 PM, Sasha Levin wrote: > On 12/21/2012 03:46 PM, Stanislav Kinsbursky wrote: >> 21.12.2012 00:47, Andrew Morton пишет: >>> On Thu, 20 Dec 2012 08:06:32 +0400 >>> Stanislav Kinsbursky<skinsbursky@...allels.com> wrote: >>> >>>> 19.12.2012 00:36, Andrew Morton __________: >>>>> On Wed, 24 Oct 2012 19:34:51 +0400 >>>>> Stanislav Kinsbursky<skinsbursky@...allels.com> wrote: >>>>> >>>>>> This respin of the patch set was significantly reworked. Most part of new API >>>>>> was replaced by sysctls (by one per messages, semaphores and shared memory), >>>>>> allowing to preset desired id for next new IPC object. >>>>>> >>>>>> This patch set is aimed to provide additional functionality for all IPC >>>>>> objects, which is required for migration of these objects by user-space >>>>>> checkpoint/restore utils (CRIU). >>>>>> >>>>>> The main problem here was impossibility to set up object id. This patch set >>>>>> solves the problem by adding new sysctls for preset of desired id for new IPC >>>>>> object. >>>>>> >>>>>> Another problem was to peek messages from queues without deleting them. >>>>>> This was achived by introducing of new MSG_COPY flag for sys_msgrcv(). If >>>>>> MSG_COPY flag is set, then msgtyp is interpreted as message number. >>>>> According to my extensive records, Sasha hit a bug in >>>>> ipc-message-queue-copy-feature-introduced.patch and Fengguang found a >>>>> bug in >>>>> ipc-message-queue-copy-feature-introduced-cleanup-do_msgrcv-aroung-msg_copy-feature.patch >>>>> >>>>> It's not obvious (to me) that these things have been identified and >>>>> fixed. What's the status, please? >>>> Hello, Andrew. >>>> Fengguang's issue was solved by "ipc: simplify message copying" I sent you. >>>> But I can't find Sasha's issue. As I remember, there was some problem in >>>> early >>>> version of the patch set. But I believe its fixed now. >>> http://lkml.indiana.edu/hypermail/linux/kernel/1210.3/01710.html >>> >>> Subject: "ipc, msgqueue: NULL ptr deref in msgrcv" >> >> Ah, yes. Thanks. >> Hi found it in initial version of code, which was significantly changed (or cleaned and simplified) by further patch series. >> And I cant find out, how this can happen, because this patch he bisect to do not modify the queue itself, while he found the >> problem in testmsg. > > I actually can't reproduce it on the latest -next. > > I was reverting the IPC changes in the past couple of weeks so that I could test the > rest of the IPC code with the fuzzer, and when I added them back in again I can't > reproduce the issue I've reported earlier. > > We can probably figure out where it got fixed by bisecting between -next trees if anyone > is interested in that. Ignore that. It just took more fuzzing to stumble on it again: [ 103.164594] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010 [ 103.168159] IP: [<ffffffff81937155>] do_msgrcv+0x205/0x540 [ 103.170031] PGD c7cd067 PUD d274067 PMD 0 [ 103.170031] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 103.170031] Dumping ftrace buffer: [ 103.170031] (ftrace buffer empty) [ 103.170031] CPU 4 [ 103.170031] Pid: 7056, comm: trinity Tainted: G W 3.7.0-next-20121221-sasha-00014-g339890c #229 [ 103.170031] RIP: 0010:[<ffffffff81937155>] [<ffffffff81937155>] do_msgrcv+0x205/0x540 [ 103.170031] RSP: 0018:ffff88000c7cfe88 EFLAGS: 00010246 [ 103.170031] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 103.170031] RDX: ffff880013681f00 RSI: 0000000000000124 RDI: ffff8800075a7810 [ 103.170031] RBP: ffff88000c7cff68 R08: 0000000000000000 R09: 0000000000000000 [ 103.170031] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000002 [ 103.170031] R13: ffff8800075a78c0 R14: 7fffffff00000000 R15: ffff8800075a7810 [ 103.170031] FS: 00007ffa529ae700(0000) GS:ffff880013c00000(0000) knlGS:0000000000000000 [ 103.170031] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 103.170031] CR2: 0000000000000010 CR3: 000000000c7cc000 CR4: 00000000000406e0 [ 103.170031] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 103.170031] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 103.170031] Process trinity (pid: 7056, threadinfo ffff88000c7ce000, task ffff88000c020000) [ 103.170031] Stack: [ 103.170031] ffff88000c7cfea8 ffff88000c020000 ffff88000c020000 ffff88000c020000 [ 103.170031] 0000000000000000 ffffffff81935e50 0000000000000008 0000000000000000 [ 103.170031] ffffffff858e91e0 0000000000000000 0000000000001001 ffff88000c020000 [ 103.170031] Call Trace: [ 103.170031] [<ffffffff81935e50>] ? load_msg+0x170/0x170 [ 103.170031] [<ffffffff8107e8c4>] ? syscall_trace_enter+0x24/0x2e0 [ 103.170031] [<ffffffff81184678>] ? trace_hardirqs_on_caller+0x118/0x140 [ 103.170031] [<ffffffff819374a0>] sys_msgrcv+0x10/0x20 [ 103.170031] [<ffffffff83cdf798>] tracesys+0xe1/0xe6 [ 103.170031] Code: 80 f5 ff ff ff 90 41 83 fc 03 74 32 41 83 fc 04 74 0c 41 83 fc 02 75 2c eb 11 0f 1f 40 00 4c 3b 73 10 7d 20 66 90 e9 94 00 00 00 <4c> 39 73 10 0f 85 8a 00 00 00 90 eb 0c 66 0f 1f 44 00 00 4c 39 [ 103.170031] RIP [<ffffffff81937155>] do_msgrcv+0x205/0x540 [ 103.170031] RSP <ffff88000c7cfe88> [ 103.170031] CR2: 0000000000000010 [ 103.228270] ---[ end trace ddc37199fdad82b0 ]--- Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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