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Re: [PATCH] [PR libc/18801] PIE binary with STT_GNU_IFUNC symbol and TEXTREL segfaults on x86_64
- From: Paul Pluzhnikov <ppluzhnikov at google dot com>
- To: Sriraman Tallam <tmsriram at google dot com>
- Cc: GLIBC Devel <libc-alpha at sourceware dot org>, Ian Lance Taylor <iant at google dot com>, David Li <davidxl at google dot com>, "H.J. Lu" <hjl dot tools at gmail dot com>
- Date: Tue, 11 Aug 2015 14:39:32 -0700
- Subject: Re: [PATCH] [PR libc/18801] PIE binary with STT_GNU_IFUNC symbol and TEXTREL segfaults on x86_64
- Authentication-results: sourceware.org; auth=none
- References: <CAAs8Hmy32PV1z0D7So6TEzFosCyJNUB_yco_6SYi=tKHUpBMQg at mail dot gmail dot com>
On Tue, Aug 11, 2015 at 2:21 PM, Sriraman Tallam <tmsriram@google.com> wrote:
> Details here:
> https://sourceware.org/bugzilla/show_bug.cgi?id=18801
>
> Thanks to Paul Pluzhnikov for identifying the problem and suggesting the fix.
I'll note that this will cause any TEXTREL binary to fail under
SELinux config that prohibits "W+E" permissions. But I think there are
few such binaries.
It's either
- make TEXTREL binary not run under SELinux, or
- make them run, but crash mysteriously if they have a called IFUNC
resolver in them (or are linked with '-z,now').
> PR 18801
> * elf/dl-reloc.c (_dl_relocate_object): Preserve the
> original permissions when protecting the segment for writing it.
> * sysdeps/x86_64/Makefile (ifunc-pie-txtrel-test): New test.
> * sysdeps/x86_64/tst-pie-ifunc-txtrel.S: New file.
The canonical ChangeLog entry format is:
2015-08-11 Sriraman Tallam <tmsriram@google.com>
Paul Pluzhnikov <ppluzhnikov@google.com>
[BZ #18801]
* elf/dl-reloc.c (_dl_relocate_object): Don't remove execute
permissions when making segment writable.
* sysdeps/x86_64/Makefile (ifunc-pie-txtrel-test): New test.
* sysdeps/x86_64/tst-pie-ifunc-txtrel.S: New file.
--
Paul Pluzhnikov