Staging
v0.8.1
https://github.com/torvalds/linux
Revision 8d6c83f0ba5e1bd1e8bb2e3c7de4c276dc247f99 authored by KOSAKI Motohiro on 19 August 2010, 21:13:39 UTC, committed by Linus Torvalds on 20 August 2010, 16:34:55 UTC
dump_tasks() needs to hold the RCU read lock around its access of the
target task's UID.  To this end it should use task_uid() as it only needs
that one thing from the creds.

The fact that dump_tasks() holds tasklist_lock is insufficient to prevent the
target process replacing its credentials on another CPU.

Then, this patch change to call rcu_read_lock() explicitly.

	===================================================
	[ INFO: suspicious rcu_dereference_check() usage. ]
	---------------------------------------------------
	mm/oom_kill.c:410 invoked rcu_dereference_check() without protection!

	other info that might help us debug this:

	rcu_scheduler_active = 1, debug_locks = 1
	4 locks held by kworker/1:2/651:
	 #0:  (events){+.+.+.}, at: [<ffffffff8106aae7>]
	process_one_work+0x137/0x4a0
	 #1:  (moom_work){+.+...}, at: [<ffffffff8106aae7>]
	process_one_work+0x137/0x4a0
	 #2:  (tasklist_lock){.+.+..}, at: [<ffffffff810fafd4>]
	out_of_memory+0x164/0x3f0
	 #3:  (&(&p->alloc_lock)->rlock){+.+...}, at: [<ffffffff810fa48e>]
	find_lock_task_mm+0x2e/0x70

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent b52723c
Raw File
Tip revision: 8d6c83f0ba5e1bd1e8bb2e3c7de4c276dc247f99 authored by KOSAKI Motohiro on 19 August 2010, 21:13:39 UTC
oom: __task_cred() need rcu_read_lock()
Tip revision: 8d6c83f
REPORTING-BUGS
[Some of this is taken from Frohwalt Egerer's original linux-kernel FAQ]

     What follows is a suggested procedure for reporting Linux bugs. You
aren't obliged to use the bug reporting format, it is provided as a guide
to the kind of information that can be useful to developers - no more.

     If the failure includes an "OOPS:" type message in your log or on
screen please read "Documentation/oops-tracing.txt" before posting your
bug report. This explains what you should do with the "Oops" information
to make it useful to the recipient.

      Send the output to the maintainer of the kernel area that seems to
be involved with the problem, and cc the relevant mailing list. Don't
worry too much about getting the wrong person. If you are unsure send it
to the person responsible for the code relevant to what you were doing.
If it occurs repeatably try and describe how to recreate it. That is
worth even more than the oops itself.  The list of maintainers and
mailing lists is in the MAINTAINERS file in this directory.  If you
know the file name that causes the problem you can use the following
command in this directory to find some of the maintainers of that file:
     perl scripts/get_maintainer.pl -f <filename>

      If it is a security bug, please copy the Security Contact listed
in the MAINTAINERS file.  They can help coordinate bugfix and disclosure.
See Documentation/SecurityBugs for more information.

      If you are totally stumped as to whom to send the report, send it to
linux-kernel@vger.kernel.org. (For more information on the linux-kernel
mailing list see http://www.tux.org/lkml/).

This is a suggested format for a bug report sent to the Linux kernel mailing
list. Having a standardized bug report form makes it easier for you not to
overlook things, and easier for the developers to find the pieces of
information they're really interested in. Don't feel you have to follow it.

      First run the ver_linux script included as scripts/ver_linux, which
reports the version of some important subsystems.  Run this script with
the command "sh scripts/ver_linux".

Use that information to fill in all fields of the bug report form, and
post it to the mailing list with a subject of "PROBLEM: <one line
summary from [1.]>" for easy identification by the developers.

[1.] One line summary of the problem:
[2.] Full description of the problem/report:
[3.] Keywords (i.e., modules, networking, kernel):
[4.] Kernel information
[4.1.] Kernel version (from /proc/version):
[4.2.] Kernel .config file:
[5.] Most recent kernel version which did not have the bug:
[6.] Output of Oops.. message (if applicable) with symbolic information
     resolved (see Documentation/oops-tracing.txt)
[7.] A small shell script or example program which triggers the
     problem (if possible)
[8.] Environment
[8.1.] Software (add the output of the ver_linux script here)
[8.2.] Processor information (from /proc/cpuinfo):
[8.3.] Module information (from /proc/modules):
[8.4.] Loaded driver and hardware information (/proc/ioports, /proc/iomem)
[8.5.] PCI information ('lspci -vvv' as root)
[8.6.] SCSI information (from /proc/scsi/scsi)
[8.7.] Other information that might be relevant to the problem
       (please look in /proc and include all information that you
       think to be relevant):
[X.] Other notes, patches, fixes, workarounds:


Thank you
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