From: nagachika00@gmail.com
To: ruby-core@ruby-lang.org
Subject: [ruby-core:94411] [Ruby master Bug#14834] rb_profile_frames SEGV when PC adjusted on IFUNC
Date: Sun, 18 Aug 2019 06:10:52 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-80833.20190818061051.5b6fc1f24291c6f7@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-14834.20180608050715@ruby-lang.org
Issue #14834 has been updated by nagachika (Tomoyuki Chikanaga).
Backport changed from 2.4: DONTNEED, 2.5: DONTNEED, 2.6: REQUIRED to 2.4: DONTNEED, 2.5: DONTNEED, 2.6: DONE
ruby_2_6 r67745 merged revision(s) 5d33f787169bcc3594d2264726695d58c4a06899,8b162ce9d1003e4e469d8f48cb9a2076fd45b47c.
----------------------------------------
Bug #14834: rb_profile_frames SEGV when PC adjusted on IFUNC
https://bugs.ruby-lang.org/issues/14834#change-80833
* Author: kivikakk (Ashe Connor)
* Status: Closed
* Priority: Normal
* Assignee: shyouhei (Shyouhei Urabe)
* Target version:
* ruby -v: ruby 2.6.0dev (2018-06-08 trunk 63606) [x86_64-linux]
* Backport: 2.4: DONTNEED, 2.5: DONTNEED, 2.6: DONE
----------------------------------------
Since r62052, we increment `ec->cfp->pc` by one pointer width (e.g. 8 bytes) in `gc_event_hook_body` around the `EXEC_EVENT_HOOK` call.
This becomes a problem when the hook is on an IFUNC: in this case, `pc == 0x0`, meaning we increment it to a non-zero value during that call.
`rb_profile_frames` uses the following check to determine if frame info should be recorded:
~~~ c
if (cfp->iseq && cfp->pc) {
~~~
The example here is [`stackprof`](https://github.com/tmm1/stackprof/blob/58d65ffa801ed27f013d573148783694526c7426/ext/stackprof/stackprof.c#L486), which calls `rb_profile_frames` in a gc event hook. This will segfault currently, as the above check will pass.
`calc_lineno` then attempts to calculate the line number:
~~~ c
size_t pos = (size_t)(pc - iseq->body->iseq_encoded);
~~~
This fails for a variety of reasons: `iseq_encoded` isn't valid because `iseq` isn't an `rb_iseq_t` underneath, producing an essentially random value, and `pc` is 0x8, so we underflow and eventually cause an overrun in `succ_index_lookup` with a huge `pos` argument.
We instead only adjust PC if it appears to be a valid pointer in the first place.
---Files--------------------------------
pc-treatment.diff (777 Bytes)
--
https://bugs.ruby-lang.org/
prev parent reply other threads:[~2019-08-18 6:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-14834.20180608050715@ruby-lang.org>
2018-06-08 5:07 ` [ruby-core:87449] [Ruby trunk Bug#14834] rb_profile_frames SEGV when PC adjusted on IFUNC ashe
2018-06-08 5:13 ` [ruby-core:87450] " ashe
2018-06-08 5:44 ` [ruby-core:87451] " ashe
2018-06-08 8:13 ` [ruby-core:87453] [Ruby trunk Bug#14834][Assigned] " shyouhei
2018-06-25 5:47 ` [ruby-core:87628] [Ruby trunk Bug#14834] " ashe
2018-06-27 0:16 ` [ruby-core:87648] " shyouhei
2019-07-30 16:04 ` [ruby-core:94057] [Ruby master " john
2019-08-01 7:09 ` [ruby-core:94091] " shyouhei
2019-08-01 17:30 ` [ruby-core:94099] " tenderlove
2019-08-02 19:41 ` [ruby-core:94117] " XrXr
2019-08-18 6:10 ` nagachika00 [this message]
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