From: Ken Brown <kbrown@cornell.edu>
To: cygwin-patches@cygwin.com
Subject: Re: [PATCH] fhandler_pipe: add sanity limit to handle loops
Date: Fri, 24 Dec 2021 12:17:08 -0500 [thread overview]
Message-ID: <c5115e9b-6475-d30e-04d3-cb84cfa92b3a@cornell.edu> (raw)
In-Reply-To: <alpine.BSO.2.21.2112231623490.11760@resin.csoft.net>
On 12/23/2021 7:29 PM, Jeremy Drake via Cygwin-patches wrote:
> On Thu, 23 Dec 2021, Ken Brown wrote:
>
>>> - for (ULONG j = 0; j < phi->NumberOfHandles; j++)
>>> + for (ULONG j = 0; j < min(phi->NumberOfHandles, n_handle); j++)
>>
>> Reading the preceding code, I don't see how n_handle could be less than
>> phi->NumberOfHandles. Can you explain?
>>
>
> Not really. I saw this stack trace:
> ...
> #3 0x0000000180062f13 in exception::handle (e=0x14cc4f0, frame=<optimized out>, in=<optimized out>, dispatch=<optimized out>) at /c/S/msys2-runtime/src/msys2-runtime/winsup/cygwin/exceptions.cc:835
> #4 0x00007ff8abd320cf in ntdll!.chkstk () from /c/Windows/SYSTEM32/ntdll.dll
> #5 0x00007ff8abce1454 in ntdll!RtlRaiseException () from /c/Windows/SYSTEM32/ntdll.dll
> #6 0x00007ff8abd30bfe in ntdll!KiUserExceptionDispatcher () from /c/Windows/SYSTEM32/ntdll.dll
> #7 0x0000000180092687 in fhandler_pipe::get_query_hdl_per_process (this=this@entry=0x1803700f8, name=name@entry=0x14cc820 L"\\Device\\NamedPipe\\dd50a72ab4668b33-10348-pipe-nt-0x6E6", ntfn=ntfn@entry=0x8000c2ce0) at /c/S/msys2-runtime/src/msys2-runtime/winsup/cygwin/fhandler_pipe.cc:1281
> #8 0x0000000180092bdb in fhandler_pipe::temporary_query_hdl (this=this@entry=0x1803700f8) at /c/S/msys2-runtime/src/msys2-runtime/winsup/cygwin/fhandler_pipe.cc:1190
> ...
>
> Line 1281 of fhandler_pipe.cc was
> if (phi->Handles[j].GrantedAccess != access)
>
> The only way I could see that causing an exception was if it was reading
> past the end of the allocated memory, if j was greater than (or equal to)
> n_handle. Unfortunately, I haven't been able to catch it in a debugger
> again, so I can't confirm this. I took a core with 'dumper' but gdb
> doesn't want to load it (it says Core file format not supported, maybe
> something with msys2's gdb?).
I agree that it's hard to see how the line you quoted could cause an exception.
But you were using an optimized build, so I'm not sure how reliable the
line-number information is.
Is it feasible to run your test under strace? If so, you could add some
debug_printf statements to examine the values of n_handle and
phi->NumberOfHandles. Or what about simply adding an assertion that
phi->NumberOfHandles <= n_handle?
Ken
next prev parent reply other threads:[~2021-12-24 17:17 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-23 23:10 Jeremy Drake
2021-12-24 0:06 ` Ken Brown
2021-12-24 0:29 ` Jeremy Drake
2021-12-24 17:17 ` Ken Brown [this message]
2021-12-24 19:42 ` Jeremy Drake
2021-12-24 22:46 ` Ken Brown
2021-12-24 23:42 ` Jeremy Drake
2021-12-25 0:39 ` Jeremy Drake
2021-12-25 3:19 ` Takashi Yano
2021-12-25 3:47 ` Jeremy Drake
2021-12-25 4:12 ` Takashi Yano
2021-12-25 5:40 ` Jeremy Drake
2021-12-25 17:10 ` Takashi Yano
2021-12-25 17:16 ` Takashi Yano
2021-12-25 19:00 ` Marco Atzeri
2021-12-25 19:20 ` Jeremy Drake
2021-12-25 22:18 ` Ken Brown
2021-12-25 23:00 ` Jeremy Drake
2021-12-26 3:04 ` Ken Brown
2021-12-26 4:56 ` Jeremy Drake
2021-12-26 15:09 ` Ken Brown
2021-12-26 16:04 ` Ken Brown
2021-12-26 16:24 ` Ken Brown
2021-12-26 21:35 ` Jeremy Drake
2021-12-26 22:18 ` Ken Brown
2021-12-26 22:43 ` Jeremy Drake
2021-12-26 23:12 ` Ken Brown
2021-12-26 23:23 ` Jeremy Drake
2021-12-27 2:42 ` Ken Brown
2021-12-27 21:12 ` Jeremy Drake
2021-12-29 21:59 ` Ken Brown
2021-12-29 23:29 ` Jeremy Drake
2021-12-27 20:01 ` Jon Turney
2021-12-29 5:45 ` Jeremy Drake
2021-12-30 15:44 ` Jon Turney
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