Fix POSIX mqueue open issue
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- v1 Latest8 patches 12 repliesIn review
Patches in v1 No applies recorded yet
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 1/8 | ipc/mqueue: cleanup definition names and locationsinclude/ ipc/ | +13 | 2 replies | |
| 2/8 | ipc/mqueue: switch back to using non-max values on createinclude/ ipc/ | +5 | 4 replies | |
| 3/8 | ipc/mqueue: enforce hard limitsipc/ | +5 | 0 replies | |
| 4/8 | ipc/mqueue: update maximums for the mqueue subsysteminclude/ ipc/ | +43 | 0 replies | |
| 5/8 | mqueue: revert bump up DFLT_*MAXinclude/ | +3 | 4 replies | |
| 6/8 | mqueue: don't use kmalloc with KMALLOC_MAX_SIZEipc/ | +2 | 1 reply | |
| 7/8 | mqueue: separate mqueue default value from maximum value v2Documentation/ include/ ipc/ +1 more | +33 | 1 reply | |
| 8/8 | selftests: add mq_open_teststools/ tools/ tools/ | +501 | 0 replies |
Reviews trailers per patch
4 of 8 patches have a Reviewed-by or Acked-by.
| Patch | Doug Ledford | Joe Korty | Serge Hallyn |
|---|---|---|---|
| 1/8 | A-b | ||
| 2/8 | |||
| 3/8 | |||
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| 5/8 | A-b | A-b | A-b |
| 6/8 | A-b | A-b | |
| 7/8 | A-b | A-b | A-b |
| 8/8 |
Trailers given in replies are filled; those carried in the patches from earlier versions are outlined with dashes. Scroll the table sideways for all 3 reviewers.
Cover letter [Patch 0/8] Fix POSIX mqueue open issue
Quoted 8 lines · Andrew Morton
Quoted 1 line · On Wed, 14 Mar 2012 17:28:33 -0400 Doug Ledford <[email protected]> wrote:
This has obviously fallen through the cracks.
It sure has. Please dig out whatever is the currently favored patchset, refresh, retest and resend, with changelogging which fully covers the reasoning and decision process?
Done.
Quoted 5 lines
Quoted 3 lines
so that if there are any apps out there that have been coded to expect this behavior, then there is a workaround path for them until they get coded
We'll be especially interested in the implications of this part.
The implications are this. Since commit b231cca4381 on Oct 18, 2008, calls to mq_open() that did not pass in an attribute struct and expected to get default values for the size of the queue and the max message size now get the system wide maximums instead of hardwired defaults like they used to get.
This was uncovered when one of the earlier patches in this patch set increased the default system wide maximums at the same time it increased the hard ceiling on the system wide maximums (a customer specifically needed the hard ceiling brought back up, the new ceiling that commit b231cca4381 introduced was too low for their production systems). By increasing the default maximums and not realising they were tied to any attempt to create a message queue without an attribute struct, I had inadvertently made it such that all message queue creation attempts without an attribute struct were failing because the new default maximums would create a queue that exceeded the default rlimit for message queue bytes.
As a result, the system wide defaults were brought back down to their previous levels, and the system wide ceilings on the maximums were raised to meet the customer's needs. However, the fact that the no attribute struct behavior of mq_open() could be broken by changing the system wide maximums for message queues was seen as fundamentally broken itself. So we hardwired the no attribute case back like it used to be. But, then we realized that on the very off chance that some piece of software in the wild depended on that behavior, we could work around that issue by adding two new knobs to /proc that allowed setting the defaults for message queues created without an attr struct separately from the system wide maximums.
What is not an option IMO is to leave the current behavior in place. No piece of software should ever rely on setting the system wide maximums in order to get a desired message queue. Such a reliance would be so fundamentally multitasking OS unfriendly as to not really be tolerable. Fortunately, we don't know of any software in the wild that uses this except for a regression test program that caught the issue in the first place. If there is though, we have made accommodations with the two new /proc knobs (and that's all the accommodations such fundamentally broken software can be allowed)..
Doug Ledford (5):
ipc/mqueue: cleanup definition names and locations ipc/mqueue: switch back to using non-max values on create ipc/mqueue: enforce hard limits
ipc/mqueue: update maximums for the mqueue subsystem
selftests: add mq_open_tests
KOSAKI Motohiro (3):
mqueue: revert bump up DFLT_*MAX
mqueue: don't use kmalloc with KMALLOC_MAX_SIZE
mqueue: separate mqueue default value from maximum value v2
Documentation/sysctl/fs.txt | 7 + include/linux/ipc_namespace.h | 42 ++- ipc/mq_sysctl.c | 49 ++-- ipc/mqueue.c | 26 +- tools/testing/selftests/Makefile | 2 +- tools/testing/selftests/mqueue/Makefile | 8 + tools/testing/selftests/mqueue/mq_open_tests.c | 492 ++++++++++++++++++++++++ 7 files changed, 590 insertions(+), 36 deletions(-) create mode 100644 tools/testing/selftests/mqueue/Makefile create mode 100644 tools/testing/selftests/mqueue/mq_open_tests.c
Signature · 1 line
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