From: Thomas Wolff <towo@towo.net>
To: cygwin-developers@cygwin.com
Subject: Re: cygwin_create_path causes null pointer crashes
Date: Mon, 12 Dec 2016 19:28:00 -0000 [thread overview]
Message-ID: <3a85ca92-2959-9963-1934-4e3f4e448cf1@towo.net> (raw)
In-Reply-To: <20161211110806.GA22664@calimero.vinschen.de>
Hi Corinna,
Am 11.12.2016 um 12:08 schrieb Corinna Vinschen:
> Hi Thomas,
>
> On Dec 10 03:03, Thomas Wolff wrote:
>> cygwin_create_path is supposed to call malloc itself,
>> however, it occasionally returns with null and errno == ENOSPC,
>> if it's provided with a network path, e.g.
>> cygwin_create_path(CCP_POSIX_TO_WIN_W, "/cygdrive/s/.config/mintty")
>> returns null in ~ 3 of 1000 cases, where /cygdrive/s exists but
>> /cygdrive/s/.config does not
> Did you try to debug and fix the issue? This is the developer's mailing
> list after all...
I can contribute some initial analysis:
Cloning cygwin_create_path from cygwin/path.cc with these essentials:
ssize_t size = cygwin_conv_path (what, from, NULL, 0);
// checking size, calling malloc
if (cygwin_conv_path (what, from, to, size) == -1)
...
there are actually two different errors happening, with example path
"/cygdrive/s/.config/mintty":
1. the first call (for size determination) returns 44 but the second
call returns the correct result "S:\.config\mintty".
2. the first call returns 36 but the second call (provided with a larger
size value patched into the function) returns "S:\.config\mintty.lnk"
(which needs 44 bytes); this is obviously the call that would return
null if not patched with a faked buffer size
Another observation, by the slowness of the calls, is that apparently
the drive is actually accessed during the path conversion, which I
wouldn't have expected from a plain path conversion function.
The underlying function cygwin_conv_path looks a bit complicated for a
straight-forward analysis to me...
------
Thomas
next prev parent reply other threads:[~2016-12-12 19:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-10 2:03 Thomas Wolff
2016-12-11 11:08 ` Corinna Vinschen
2016-12-12 19:28 ` Thomas Wolff [this message]
2016-12-13 11:57 ` Corinna Vinschen
2016-12-14 20:25 ` Thomas Wolff
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