|Summary:||ptrace(PTRACE_CONT, sig) kills app even if sig is blocked|
|Product:||Red Hat Enterprise Linux 5||Reporter:||Tom Fleck <tjf>|
|Component:||kernel||Assignee:||Jerome Marchand <jmarchan>|
|Status:||CLOSED ERRATA||QA Contact:||Red Hat Kernel QE team <kernel-qe>|
|Version:||5.1||CC:||dvlasenk, dzickus, imatusov, roland|
|Fixed In Version:||Doc Type:||Bug Fix|
|Doc Text:||Story Points:||---|
|Last Closed:||2009-09-02 08:58:46 UTC||Type:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
Description Tom Fleck 2008-06-17 19:29:57 UTC
There was apparently a significant change in ptrace behavior somewhere between 2.6.9 (e.g., RHEL4) and 2.6.18 (e.g., RHEL5) that I couldn't find documented anywhere: ptrace(PTRACE_CONT, application_pid, 0, SIGUSR1) will terminate the application even if the application has SIGUSR1 blocked, whereas ptrace(PTRACE_CONT, application_pid, 0, 0); kill (application_pid, SIGUSR1); will not. Is this a bug or a feature, and when was it introduced? The attached pair of test programs below demonstrate this. Thanks! ...Tom
Comment 1 Tom Fleck 2008-06-17 19:29:57 UTC
Created attachment 309666 [details] test case: 2 1-file C programs
Comment 2 Jerome Marchand 2009-01-09 15:59:10 UTC
Created attachment 328559 [details] proposed patch When the signal to deliver is blocked, use a traditional signal in ptrace_induce_signal() instead of forcefully inject it with utrace_inject_signal().
Comment 3 Denys Vlasenko 2009-01-18 00:28:29 UTC
Made a testcase for this bug, ptrace_cont-defeats-sigblock.c: http://sources.redhat.com/cgi-bin/cvsweb.cgi/~checkout~/tests/ptrace-tests/tests/ptrace_cont-defeats-sigblock.c?content-type=text/plain&cvsroot=systemtap
Comment 4 Jerome Marchand 2009-01-21 14:03:07 UTC
I forgot to signal the patch was posted on rhkl: http://post-office.corp.redhat.com/archives/rhkernel-list/2009-January/msg00459.html
Comment 5 Denys Vlasenko 2009-02-05 14:25:14 UTC
Jerome, if signal is blocked, your patch does prevent signal from being raised, but doesn't it accidentally also forget to make signal pending? IOW: if process will later unblock this signal, will it be immediately raised?
Comment 6 Jerome Marchand 2009-02-05 14:45:43 UTC
If that signal is blocked, the signal is send through the traditional send_sig() function which will make that signal pending. The test case posted in first comment test that and is successful on patched kernel. Have you noticed any problem with your test case?
Comment 7 Denys Vlasenko 2009-02-06 16:20:17 UTC
No, it was an off-the-cuff comment. Sorry for adding noise. :(
Comment 8 Denys Vlasenko 2009-02-06 16:43:38 UTC
I updated ptrace_cont-defeats-sigblock.c testcase to also check whether signal gets remembered, and whether it will be raised when signal mask is cleared.
Comment 9 RHEL Product and Program Management 2009-02-11 10:09:58 UTC
This request was evaluated by Red Hat Product Management for inclusion in a Red Hat Enterprise Linux maintenance release. Product Management has requested further review of this request by Red Hat Engineering, for potential inclusion in a Red Hat Enterprise Linux Update release for currently deployed products. This request is not yet committed for inclusion in an Update release.
Comment 10 RHEL Product and Program Management 2009-02-16 15:45:49 UTC
Updating PM score.
Comment 11 Don Zickus 2009-03-04 19:59:27 UTC
in kernel-2.6.18-133.el5 You can download this test kernel from http://people.redhat.com/dzickus/el5 Please do NOT transition this bugzilla state to VERIFIED until our QE team has sent specific instructions indicating when to do so. However feel free to provide a comment indicating that this fix has been verified.
Comment 13 Tom Fleck 2009-03-04 21:17:08 UTC
(In reply to comment #11) > in kernel-2.6.18-133.el5 > You can download this test kernel from http://people.redhat.com/dzickus/el5 Not there yet?
Comment 14 Don Zickus 2009-03-04 22:21:00 UTC
sorry I suck today. the rpms are uploading right now. thanks for catching that. -Don
Comment 16 errata-xmlrpc 2009-09-02 08:58:46 UTC
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2009-1243.html