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Date: Tue, 29 Sep 2020 16:34:07 -0400
From: Rich Felker <dalias@...c.org>
To: Jesse Hathaway <jesse@...ki-mvuki.org>
Cc: musl@...ts.openwall.com
Subject: Re: Re: Pending patches for MT-fork stuff
On Tue, Sep 29, 2020 at 01:51:30PM -0500, Jesse Hathaway wrote:
> On Tue, Sep 29, 2020 at 1:36 PM Rich Felker <dalias@...c.org> wrote:
> > Can you provide an strace (with -f) showing the hang? It's probably
> > not related to this since fork does not seem to be involved. Depending
> > on how you're using Go, it may just be Go bypassing libc then trying
> > to use libc functions, which at least used to be a big problem; I
> > don't know if it's fixed nowadays or not.
>
> Thanks Rich, for taking a look, I have attached an strace of the
> program compiled against musl & glibc. The first call to setreuid
> succeeds in both, but the second call fails under musl. Jesse
The problem is this line:
> 8238 rt_sigprocmask(SIG_SETMASK, ~[HUP INT QUIT ILL TRAP ABRT BUS FPE SEGV TERM STKFLT CHLD PROF SYS RTMIN RT_1], <unfinished ...>
Something broken in the Go runtime is bypassing libc and either
calling SYS_rt_sigprocmask itself, or calling the libc sigprocmask
function with a sigset_t it produced itself, blocking a libc-internal
signal. This makes it invalid to make any further use of libc.
Either it (the Go runtime) needs to manipulate sigset_t objects via
the public APIs for them (sigfillset, sigaddset, etc.) or its wrapper
for sigprocmask needs to convert the Go-manipulated sigset_t to one
valid for libc by iterating over the bits and using sigaddset, so that
invalid bits don't end up in the one passed to libc.
Rich
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