Re: Heads up: *possible* bug in cygwin

[Charles Wilson <cwilson at ece dot gatech dot edu>]

Steven O'Brien wrote:
> Hi
> I found a possible glib buffer overflow that is cygwin-specific (due to
> a bug in cygwin perhaps?) that I worked around when porting glib-1.2.10
> to cygwin. Maybe this is still a problem in glib-2.0.x
> From (hazy) memory, the buffer is 64 bytes, so if your /etc/passwd entry
> has more than 64 chars (quite possible if you are using ntsec) then
> memory gets trashed.
>
> My patch works around this problem by allocating a buffer of 1024 bytes
> for cygwin. I think I got this value by reading the cygwin dll source to
> find a real upper bound, but it was a long time ago so this needs
> checking. 
I saw this...it's probably a decent workaround, but hasn't yet been 
accepted into current glib source AFAICT --- glib-2.2.0 still uses a 64 
byte buffer for reading pw entries.  But that's not where the segfault 
is happening in my case (as my earlier message showed).

> Of course a real fix is required to sysconf() /  getpwuid_r() in cygwin,
I'm not sure about that -- is there some POSIX limitation on the number 
of bytes that getpwuid_r() is allowed to return?  I think existing code 
that hardcodes a 64 byte limit is just using that magic number because 
it "works on linux" (and hpux/solaris/etc)

> but to test this theory you could borrow the fix from my glib patch and
> try it on glib 2.0.x
Most of the patches I *did* use were from your 1.2.x work. :-)

--Chuck


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