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Date: Sat, 27 Feb 2021 09:13:17 -0800
From: Khem Raj <raj.khem@...il.com>
To: musl@...ts.openwall.com
Cc: Dominic Chen <d.c.ddcc@...il.com>
Subject: Re: fdopen() doesn't check for valid fd
On Fri, Feb 26, 2021 at 10:01 AM Rich Felker <dalias@...c.org> wrote:
>
> On Fri, Feb 26, 2021 at 12:36:19PM -0500, Dominic Chen wrote:
> > I've been verifying the behavior of an application between glibc and
> > musl, and have noticed that the musl implementation of fdopen()
> > assumes that the input fd is valid, whereas glibc does not. Per
> > https://pubs.opengroup.org/onlinepubs/9699919799/, it seems that
> > fdopen() is allowed to fail with EBADF, so inside __fdopen(), the
> > syscalls to SYS_fcntl and SYS_ioctl should probably check for an
> > error, deallocate the FILE *, and return nullptr.
>
> This is specified as a "may fail" error not a "shall fail". It was
> discussed before (I can look up the old thread if you're interested)
> and there are some paths in which checking for it would be free, but
> others where it would not, and it would require reorganizing the
> function's flow in a way that's less desirable in one way or another,
> so it doesn't seem like a good idea for the sake of something a caller
> can't actually use.
>
perhaps we should add it to differences with glibc document [1]
> Rich
[1] https://wiki.musl-libc.org/functional-differences-from-glibc.html
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