From: Jan Kratochvil <jan.kratochvil@redhat.com>
To: Chet Ramey <chet.ramey@case.edu>
Cc: bug-readline@gnu.org, gdb-patches@sourceware.org,
saugustine@google.com, chet@po.cwru.edu
Subject: Re: [Bug-readline] [readline patch, gdb-7.3?] Avoid free from a signal handler [Re: [PATCH] Make interrupting tab-completion safe.]
Date: Wed, 06 Jul 2011 17:42:00 -0000 [thread overview]
Message-ID: <20110706164400.GA31447@host1.jankratochvil.net> (raw)
In-Reply-To: <110706155826.AA07325.SM@caleb.INS.CWRU.Edu>
On Wed, 06 Jul 2011 17:58:26 +0200, Chet Ramey wrote:
> As I said, I'm willing to remove these references and see what happens. Since
> you have a way to readily reproduce the problem, I was hoping you'd do it
> and let me know what you found.
I do not think any testing matters here. This is a difficult to reproduce
race + memory corruption. While a crash proves it is wrong no crash does not
prove anything.
Even if no existing system ever crashes the code is still wrong because it
violates POSIX:
http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html
The following table defines a set of functions that shall be either
reentrant or non-interruptible by signals and shall be async-signal-safe.
Static code analysis is the only valid verification. Currently the signal
code calls free() which is not listed in the safe syscalls list above,
therefore the code is not correct.
I do not know if it is possible to code _rl_handle_signal in a way which uses
only the safe syscalls and only atomic operations on volatile data structures.
Anyway even if it would be possible I find such code very fragile and
I believe the signals should be always delayed through _rl_caught_signal.
Sure it then has to depend on the application which should properly return to
readline callers immediately if it sees any EINTR.
Thanks,
Jan
next prev parent reply other threads:[~2011-07-06 17:32 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-11 0:19 [PATCH] Make interrupting tab-completion safe Sterling Augustine
2011-06-12 12:12 ` Jan Kratochvil
2011-06-13 17:45 ` Sterling Augustine
2011-06-26 22:22 ` [readline patch, gdb-7.3?] Avoid free from a signal handler [Re: [PATCH] Make interrupting tab-completion safe.] Jan Kratochvil
2011-06-27 16:03 ` Joel Brobecker
2011-06-29 21:49 ` Jan Kratochvil
2011-06-29 13:54 ` [Bug-readline] " Chet Ramey
2011-06-29 20:35 ` Jan Kratochvil
2011-06-30 14:38 ` Chet Ramey
2011-07-06 16:03 ` Jan Kratochvil
2011-07-06 16:07 ` Chet Ramey
2011-07-06 17:42 ` Jan Kratochvil [this message]
2011-07-07 13:40 ` Chet Ramey
2011-07-08 16:03 ` Chet Ramey
2011-10-19 20:30 ` Jan Kratochvil
2011-10-19 17:02 ` Jan Kratochvil
2011-10-19 17:51 ` Pedro Alves
2011-10-19 18:50 ` Chet Ramey
2011-07-11 18:53 ` [PATCH] Make interrupting tab-completion safe Sterling Augustine
2011-07-11 18:54 ` Jan Kratochvil
[not found] ` <CAEG7qUxFvEoJ-E2YsoFPL-tKoK4kD3-pKn-h31uUeXQoDD2Gaw@mail.gmail.com>
2011-07-12 15:59 ` [dwarf2_mark_helper patch] " Jan Kratochvil
2011-07-12 17:48 ` Sterling Augustine
2011-07-12 18:56 ` Jan Kratochvil
2011-07-12 21:18 ` [commit] " Jan Kratochvil
2011-07-12 21:42 ` Tom Tromey
2011-07-12 22:51 ` Jan Kratochvil
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110706164400.GA31447@host1.jankratochvil.net \
--to=jan.kratochvil@redhat.com \
--cc=bug-readline@gnu.org \
--cc=chet.ramey@case.edu \
--cc=chet@po.cwru.edu \
--cc=gdb-patches@sourceware.org \
--cc=saugustine@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox