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Message-ID: <87fsjqeek8.fsf@oldenburg.str.redhat.com>
Date: Mon, 27 Jun 2022 09:44:07 +0200
From: Florian Weimer <fweimer@...hat.com>
To: "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>
Cc: musl@...ts.openwall.com
Subject: Re: BUG: Calling readdir/dirfd after vfork will cause deadlock.
* Alex Xu:
> Excerpts from Nick Peng's message of June 24, 2022 11:40 pm:
>> Description: After vfork, calling functions such as readdir/dirfd may
>> cause deadlock. GNU C is OK.
>
> This is not a bug. TFM:
>
> DESCRIPTION
> Standard description
> (From POSIX.1) The vfork() function has the same effect as
> fork(2), except that the behavior is undefined if the process
> created by vfork() either modifies any data other than a variable
> of type pid_t used to store the return value from vfork(), or
> returns from the function in which vfork() was called, or calls
> any other function before successfully calling _exit(2) or one of
> the exec(3) family of functions.
>
> It may happen to appear to work in some cases on some libcs, or kernels,
> or architectures, or it may deadlock, corrupt data, or cause demons to
> fly out your nose. Do not use vfork in this manner. Avoid using fork in
> this manner either; that may work in musl 1.2.2+, and appear to work in
> glibc (but sometimes randomly corrupt data), but is not portable to
> other libcs.
Could you describe the memory corruption you have seen with
opendir/readdir on glibc?
Thanks,
Florian
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