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From: "noloader at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c/103863] New: We need a warning for loss of no-exec stacks
Date: Thu, 30 Dec 2021 01:59:55 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103863

            Bug ID: 103863
           Summary: We need a warning for loss of no-exec stacks
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: noloader at gmail dot com
  Target Milestone: ---

Hello,

This is a feature request.

For targets that support no-exec stacks, we need a warning when GCC generat=
es
code or drives the linker with loss of no-exec stacks.

The warning would be beneficial for most builds nowadays since no-exec stac=
ks
are part of most distro hardening. For example, Debian and Fedora both
incorporate it into their build system; and special steps must be taken to
avoid no-exec stacks out of the box.

The warning would also be beneficial in cases like
https://bugzilla.redhat.com/show_bug.cgi?id=3D2035802. In the 2035802 bug, =
an ARM
machine failed to boot because libz contained executable stacks even though
they were not needed.

A specific warning for no-exec stacks is slightly different than -Wtrampoli=
nes.
While trampolines resulted in executable stacks in the past, that may not h=
old
in the future as lambdas are added to the language. And trampolines are not=
 a
necessary precondition to get in an insecure state like the 2035802 bug sho=
ws.

It is most unfortunate that ASM files need special handling because the obj=
ect
files are marked with executable stacks by default. Maybe that should be
another bug report to change default behavior since the strategy nowadays i=
s:
no-exec stacks by default, do something special for executable stacks.

Thanks in advance.=