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Description of problem:
When setting devices.allow or devices.deny parameter of 'devices' controller, it does not accept values with multiple lines.
Version-Release number of selected component (if applicable):
2.6.32-71.el6.x86_64
How reproducible:
always
Steps to Reproduce:
1. mount -t cgroup -o devices foo /cgroup/devices
2. mkdir /cgroup/devices/test
3. /bin/echo "a *:* w
c 8:* r" > /cgroup/devices/test/devices.allow
Actual results:
$ cat /cgroup/devices/test/devices.list
a *:* rwm
Expected results:
$ cat /cgroup/devices/test/devices.list
a *:* rwm
c 8:* r
Additional info:
/bin/echo is quite important, bash built-in echo writes one line per write() system call, which is correctly interpreted by the kernel.
In other words, this strace sequence works as expected:
open("/cgroup/devices/test/devices.allow", ...) = 3
write(3, "a *:* w\n", 8) = 8
write(3, "c 8:* r\n", 8) = 8
And this one does not work, kernel parses only the first line, i.e. until first '\n', and ignores the second line:
open("/cgroup/devices/test/devices.allow", ...) = 3
write(3, "a *:* w\nc 8:* r\n", 16) = 16
The kernel should either process the whole input or the write() should return '8' as number of written characters, so application knows what is going on and can send next line (= next 8 characters).
Comment 2RHEL Program Management
2011-01-07 04:22:41 UTC
This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated
in the current release, Red Hat is unfortunately unable to
address this request at this time. Red Hat invites you to
ask your support representative to propose this request, if
appropriate and relevant, in the next release of Red Hat
Enterprise Linux. If you would like it considered as an
exception in the current release, please ask your support
representative.
This request was erroneously denied for the current release of Red Hat
Enterprise Linux. The error has been fixed and this request has been
re-proposed for the current release.
Comment 4RHEL Program Management
2011-02-01 05:53:25 UTC
This request was evaluated by Red Hat Product Management for
inclusion in the current release of Red Hat Enterprise Linux.
Because the affected component is not scheduled to be updated
in the current release, Red Hat is unfortunately unable to
address this request at this time. Red Hat invites you to
ask your support representative to propose this request, if
appropriate and relevant, in the next release of Red Hat
Enterprise Linux. If you would like it considered as an
exception in the current release, please ask your support
representative.
Comment 5RHEL Program Management
2011-02-01 18:50:40 UTC
This request was erroneously denied for the current release of
Red Hat Enterprise Linux. The error has been fixed and this
request has been re-proposed for the current release.
Comment 6RHEL Program Management
2011-04-04 02:26:57 UTC
Since RHEL 6.1 External Beta has begun, and this bug remains
unresolved, it has been rejected as it is not proposed as
exception or blocker.
Red Hat invites you to ask your support representative to
propose this request, if appropriate and relevant, in the
next release of Red Hat Enterprise Linux.
Comment 7RHEL Program Management
2011-10-07 15:16:51 UTC
Since RHEL 6.2 External Beta has begun, and this bug remains
unresolved, it has been rejected as it is not proposed as
exception or blocker.
Red Hat invites you to ask your support representative to
propose this request, if appropriate and relevant, in the
next release of Red Hat Enterprise Linux.
Comment 12RHEL Program Management
2013-04-12 02:23:35 UTC
This request was evaluated by Red Hat Product Management for
inclusion in a Red Hat Enterprise Linux release. Product
Management has requested further review of this request by
Red Hat Engineering, for potential inclusion in a Red Hat
Enterprise Linux release for currently deployed products.
This request is not yet committed for inclusion in a release.
(Cc'ing Aristeu.)
I don't think this is a good idea. The interface only deals with single command at a time. It's not supposed to have convenience features for the admins writing directly to it. It's fundamentally limited - the max input size is PAGE_SIZE and it can't handle split writes. The kernel interface files really aren't meant to be flexible and intelligent. In fact, I have no idea why it just isn't using sscanf(). Aristeu, why the manual parsing?
If something convenient is necessary, please implement a wrapper script which sanitizes input and feed the correctly formatted strings to the kernel. It can be done multiple times better and easier from userland.
Thanks.
Comment 14Aristeu Rozanski
2013-05-06 20:13:36 UTC
Good question, I have no idea. Will ask Serge Hallyn.
Comment 15Aristeu Rozanski
2013-05-06 20:21:56 UTC
About the multiline thing: it's not even a good interface because
- It could fail out of a wrong line and the user would have no idea which line
- Either the kernel keep the correct lines before it applied or it'll have to
implement rollback of the ones already applied.
It'd be a huge amount of code to replace a simple bash readline loop.
Description of problem: When setting devices.allow or devices.deny parameter of 'devices' controller, it does not accept values with multiple lines. Version-Release number of selected component (if applicable): 2.6.32-71.el6.x86_64 How reproducible: always Steps to Reproduce: 1. mount -t cgroup -o devices foo /cgroup/devices 2. mkdir /cgroup/devices/test 3. /bin/echo "a *:* w c 8:* r" > /cgroup/devices/test/devices.allow Actual results: $ cat /cgroup/devices/test/devices.list a *:* rwm Expected results: $ cat /cgroup/devices/test/devices.list a *:* rwm c 8:* r Additional info: /bin/echo is quite important, bash built-in echo writes one line per write() system call, which is correctly interpreted by the kernel. In other words, this strace sequence works as expected: open("/cgroup/devices/test/devices.allow", ...) = 3 write(3, "a *:* w\n", 8) = 8 write(3, "c 8:* r\n", 8) = 8 And this one does not work, kernel parses only the first line, i.e. until first '\n', and ignores the second line: open("/cgroup/devices/test/devices.allow", ...) = 3 write(3, "a *:* w\nc 8:* r\n", 16) = 16 The kernel should either process the whole input or the write() should return '8' as number of written characters, so application knows what is going on and can send next line (= next 8 characters).