Date: Wed, 17 Aug 2022 09:26:34 -0700 From: Elvis Pranskevichus <elvis@...edb.com> To: Rich Felker <dalias@...c.org> Cc: musl@...ts.openwall.com Subject: Re: [PATCH] ldso/dynlink: Protect LD_ env vars from getting clobbered by apps On Wednesday, August 17, 2022 8:29:05 AM PDT Rich Felker wrote: > On Tue, Aug 16, 2022 at 10:45:45PM -0700, Elvis Pranskevichus wrote: > > There is no guarantee that the environment block will remain intact. > > For example, PostgreSQL clobbers argv/environ area to implement its > > "setproctitle" emulation on non-BSD , and there is a popular > > Python library inspired by it . As a result, setting > > `LD_LIBRARY_PATH` or `LD_PRELOAD` has no effect on Postgres > > subprocesses when linking against musl. > > This is explicitly not allowed and is UB. This memory is not available > for the application to clobber, and code attempting to do that needs > to be patched out. Aside from the general principle, POSIX is very > clear in the specification of environ: > > "Any application that directly modifies the pointers to which the > environ variable points has undefined behavior." I understand that what Postgres et al are doing is a nasty hack. My thinking was that it is a question of compatibility with glibc's behavior, which seems to tolerate these shenanigans (at least with respect to `LD_*` variables. Good point regarding the allocator bringup overhead, I haven't thought of that. Thanks, Elvis
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.