Bug 832738

Summary:	sys-libs/glibc: Revisit --enable-stack-protector value
Product:	Gentoo Linux	Reporter:	Arfrever Frehtes Taifersar Arahesis <arfrever.fta>
Component:	Current packages	Assignee:	Gentoo Toolchain Maintainers <toolchain>
Status:	CONFIRMED ---
Severity:	normal	CC:	gentoo, m68k, om, sam
Priority:	Normal
Version:	unspecified
Hardware:	All
OS:	All
See Also:	https://bugs.gentoo.org/show_bug.cgi?id=609048 https://bugs.gentoo.org/show_bug.cgi?id=712356 https://sourceware.org/bugzilla/show_bug.cgi?id=24202 https://sourceware.org/bugzilla/show_bug.cgi?id=25680 https://bugs.gentoo.org/show_bug.cgi?id=817836
Whiteboard:
Package list:		Runtime testing required:	---

Description Arfrever Frehtes Taifersar Arahesis 2022-02-05 07:12:09 UTC

Recent ebuilds of sys-libs/glibc contain (e.g. https://gitweb.gentoo.org/repo/gentoo.git/tree/sys-libs/glibc/glibc-2.35.ebuild?id=7d711f502a5cf86ae5e73c466d647fed33d4ae4a#n901):
> 	case ${CTARGET} in
> 		m68k*)
> 			# setjmp() is not compatible with stack protection:
> 			# https://sourceware.org/PR24202
> 			myconf+=( --enable-stack-protector=no )
> 			;;
> 		*)
> 			# Use '=strong' instead of '=all' to protect only functions
> 			# worth protecting from stack smashes.
> 			# '=all' is also known to have a problem in IFUNC resolution
> 			# tests: https://sourceware.org/PR25680, bug #712356.
> 			myconf+=( --enable-stack-protector=$(usex ssp strong no) )
> 			;;
> 	esac


https://sourceware.org/PR24202 (affecting m68k) is fixed in >=sys-libs/glibc-2.33, so changes introduced in commit d74781e680bee416a48c648df1f8c6000da84e4d (https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=d74781e680bee416a48c648df1f8c6000da84e4d) probably can be reverted in >=sys-libs/glibc-2.33.


https://sourceware.org/PR25680 (affecting all architectures) is fixed in >=sys-libs/glibc-2.34, so changes introduced in commit 551958422d949b8e43393b6c9c00a2ce7c4cc4c6 (https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=551958422d949b8e43393b6c9c00a2ce7c4cc4c6) probably can be reverted in >=sys-libs/glibc-2.34.


If both assumptions are true, then this whole code can be simplified in >=sys-libs/glibc-2.34 into 1 line:
> 	myconf+=( --enable-stack-protector=$(usex ssp all no) )

Comment 1 James Le Cuirot gentoo-dev

2022-02-05 10:05:41 UTC

Oh cool, thanks for spotting that. I initially found the m68k bug, but I hadn't realised that slyfox had worked around it like this. I'll try changing it to "all" on m68k and see how it goes with some keywording/testing etc.

Comment 2 Larry the Git Cow gentoo-dev

2022-02-07 02:46:30 UTC

The bug has been referenced in the following commit(s):

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=f58ea78c13b6078eade21a0de13e032e9ef49854

commit f58ea78c13b6078eade21a0de13e032e9ef49854
Author:     Sam James <sam@gentoo.org>
AuthorDate: 2022-02-07 02:43:09 +0000
Commit:     Sam James <sam@gentoo.org>
CommitDate: 2022-02-07 02:45:29 +0000

    sys-libs/glibc: re-enable SSP for m68k; drop obsolete option in 2.35/9999
    
    - Re-enable SSP for m68k (it works now!) [0]
    - Drop no-op/obsolete/removed '--enable-stackguard-randomization' [1]
    
    But defer a decision on whether to make USE=ssp continue to
    mean -fstack-protector-strong or change to -fstack-protector-all now that
    test failure issues have veen fixed.
    
    [0] https://sourceware.org/PR24202
    [1] https://sourceware.org/git/?p=glibc.git;a=commit;h=f294306ba1385b096f4e4cac9146a989f1e6d1c0
    
    Bug: https://bugs.gentoo.org/832738
    Signed-off-by: Sam James <sam@gentoo.org>

 sys-libs/glibc/glibc-2.35.ebuild | 18 +++---------------
 sys-libs/glibc/glibc-9999.ebuild | 24 ++++++------------------
 2 files changed, 9 insertions(+), 33 deletions(-)

Comment 3 Arfrever Frehtes Taifersar Arahesis 2022-02-07 04:07:52 UTC

GCC can be configured with -DDEFAULT_FLAG_SSP=2 to use -fstack-protector-all by default.
  -DDEFAULT_FLAG_SSP=1 makes -fstack-protector default
  -DDEFAULT_FLAG_SSP=2 makes -fstack-protector-all default
  -DDEFAULT_FLAG_SSP=3 makes -fstack-protector-strong default
  -DDEFAULT_FLAG_SSP=4 makes -fstack-protector-explicit default

Also users can add e.g. -fstack-protector-all explicitly to CFLAGS.

Currently used value can be queried from compiler:

$ gcc                            -E -P -dM - < /dev/null | grep SSP
#define __SSP_ALL__ 2
$ gcc -fstack-protector-all      -E -P -dM - < /dev/null | grep SSP
#define __SSP_ALL__ 2
$ gcc -fstack-protector-strong   -E -P -dM - < /dev/null | grep SSP
#define __SSP_STRONG__ 3
$ gcc -fstack-protector          -E -P -dM - < /dev/null | grep SSP
#define __SSP__ 1
$ gcc -fstack-protector-explicit -E -P -dM - < /dev/null | grep SSP
#define __SSP_EXPLICIT__ 4


If there is desire to use --enable-stack-protector=strong for these users who do not enable -fstack-protector-all, then ebuilds can query compiler ($(tc-getCC) ${CPPFLAGS} ${CFLAGS}) and use --enable-stack-protector=all only when __SSP_ALL__ is defined.