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Date: Wed, 11 Nov 2020 09:56:03 -0500
From: Rich Felker <dalias@...c.org>
To: Alexey Izbyshev <izbyshev@...ras.ru>, musl@...ts.openwall.com
Subject: Re: [PATCH v2] MT fork
On Wed, Nov 11, 2020 at 12:25:00PM +0100, Szabolcs Nagy wrote:
> * Alexey Izbyshev <izbyshev@...ras.ru> [2020-11-11 09:35:22 +0300]:
> > On 2020-11-11 03:52, Rich Felker wrote:
> > > Here's a proposed first patch in series, getting rid of getdelim/stdio
> > > usage in ldso. I think that suffices to set the stage for adding
> > > __libc_malloc, __libc_free, __libc_calloc, __libc_realloc and having
> > > ldso use them.
> > >
>
> if we don't have to replicate a lot of code in ldso then this sounds good.
Indeed the ldso part of the patch it just:
+#define malloc __libc_malloc
+#define calloc __libc_calloc
+#define realloc __libc_realloc
+#define free __libc_free
That's the minimal needed to make it work. Assuming we adopt and keep
this I might also remove a bunch of ugly code in dynlink.c that
special-cases whether it's running with replaced malloc or not.
> > > +static ssize_t read_loop(int fd, void *p, size_t n)
> > > +{
> > > + unsigned char *b = p;
> > > + for (size_t l, i=0; i<n; i+=l) {
> > > + l = read(fd, b+i, n-i);
> > > + if (l<0) {
> > > + if (errno==EINTR) continue;
> > This increments `i` by a negative `l`.
Thanks Alexey for catching that!
> it's worse: l cannot be negative so the error check is ineffective.
>
> maybe it should be ssize_t? or check == -1
Yes, there are multiple problems and this was the original motivation
for using stdio -- not having to write this ugly error-prone code. But
it only has to be written and reviewed once so it shouldn't be too bad
to get it right. ssize_t should be fine. I mainly did ridiculous stuff
trying to be clever with scope of the vars.
> > > + if (fd>=0) {
> > > + size_t n = 0;
> > > + if (!fstat(fd, &st)) n = st.st_size;
> > > + sys_path = malloc(n+1);
> > > + sys_path[n] = 0;
> > `sys_path` can be NULL here.
Thanks, I meant to put that in if ((sys_path = malloc(n+1))) or
something. Will fix.
Rich
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