Re: Fix BZ #18757 (fmemopen doesn't fail with invalid modes)

[Paul Pluzhnikov <ppluzhnikov at gmail dot com>]

On Sun, Aug 9, 2015 at 7:36 PM, Mike Frysinger <vapier@gentoo.org> wrote:
> On 09 Aug 2015 15:28, Paul Pluzhnikov wrote:
>> +/* Check valid open mode.  Only "(r|w|a)\+?" are valid.  */
>
> this is not what the documentation states:

AFAICT, only "r", "w", "w+" and "a" are really used by __fmemopen, but
I overlooked the _IO_fopencookie part.

> https://www.gnu.org/software/libc/manual/html_node/String-Streams.html
>         "The argument opentype is the same as in fopen"
> https://www.gnu.org/software/libc/manual/html_node/Opening-Streams.html
>         there are various GNU extensions here, and the standard 'b' flag

Handling of 'b' in fmemopen has been removed:

https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=fdb7d390dd0d96e4a8239c46f3aa64598b90842b
I also filed https://bugzilla.kernel.org/show_bug.cgi?id=102551 to
update man7.org description ...


> so the only thing we should check is whether the first byte is [rwa].  and it
> seems to me that _IO_fopencookie (which fmemopen tails into) already does just
> that for us.

Oh, I see. The bug is that _IO_fopencookie doesn't set errno.
In addition, if _IO_fopencookie fails, we leak memory.

Revised patch attached.


2015-08-09  Paul Pluzhnikov  <ppluzhnikov@google.com>

        [BZ #18757]
        * libio/fmemopen.c (__fmemopen): Set EINVAL and don't leak memory.
        * libio/oldfmemopen.c (__old_fmemopen): Likewise.
        * libio/test-fmemopen.c (do_bz18757): New test.



-- 
Paul Pluzhnikov

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