Thanks again for the feedback.
Since you weren't cc:ed on my earlier email, I'd like to pull out my comment
at the top of the thread:
As this problem has been discovered rather late in our transition process, I
have a bit of a time crunch on my side which is not your problem, but I
would ask that whether or not the patch is ready to land, we reach a
consensus ASAP on:
- whether it is acceptable to introduce a new entry point for this on
32-bit architectures
- the name this new entry point should use (including symbol version)
- that it is acceptable to upstream that we proceed on implementing this
at the distro level in advance of the patch landing upstream.
Since all of your comments have been about the mechanics of the patch
landing, am I able to take it as agreed that libselinux will add a new entry
point of matchpathcon_filespec_add64@LIBSELINUX_3.6 in the next release, and
the rest is details?
On Tue, Feb 27, 2024 at 06:13:47PM +0100, Christian Göttsche wrote:
> On Tue, 27 Feb 2024 at 08:00, Steve Langasek <vorlon@xxxxxxxxxx> wrote:
> >
> > Thanks for the feedback.
> >
> > On Mon, Feb 26, 2024 at 06:52:10PM +0100, Christian Göttsche wrote:
> > > > > +#include <stdint.h>
> > > I needed <asm/bitsperlong.h> aswell for __BITS_PER_LONG
> > Can you tell me about the platform you were building on? In my tests, the
> > code with this patch behaved as intended on Ubuntu 24.04 pre-release with
> > glibc 2.38, on both armhf and amd64, with no additional includes required.
> Debian sid.
Ok. https://codesearch.debian.net/search?q=%3Casm%2Fbitsperlong.h%3E&literal=1
shows it's uncommon to include asm/bitsperlong directly from userspace
packages, but not unprecedented, so I'll go ahead and make that change.
> > > > > +#if _FILE_OFFSET_BITS == 64
> > > One should probably check for existence:
> > > #if defined(_FILE_OFFSET_BITS) && _FILE_OFFSET_BITS == 64
> > Should we not consider it an error if this is not defined? I can't think of
> > any reason why _FILE_OFFSET_BITS would legitimately be missing and in my
> > view it's ambiguous what we should do in this circumstance. Using the
> > define without checking for existence first implicitly gives an error if
> > it's missing. If preferred, we could be explicit as in:
> >
> > #if !defined(_FILE_OFFSET_BITS)
> > #error [...]
> > #endif
> > #if _FILE_OFFSET_BITS == 64
> > [...]
> During my testing yesterday _FILE_OFFSET_BITS was not defined by
> default (gcc-13/gcc-14/clang-18 on Debian sid).
It occurs to me that I only did a test build of libselinux itself with this
change, and maybe you're trying to build other software against it and
therefore running into the issue when including this public header. Ok,
'defined &&' it is.
> > > > > +typedef uint64_t libselinux_ino_t;
> > > > > +#if __BITS_PER_LONG < 64
> > > > > +#define matchpathcon_filespec_add matchpathcon_filespec_add64
> > > > > +#endif
> > > > > +#else
> > > > > +typedef uint32_t libselinux_ino_t;
> > > > > +#endif
> > > Is the typedef libselinux_ino_t really necessary, isn't it always just
> > > equal to ino_t?
> > When _FILE_OFFSET_BITS == 64, ino_t is a 64-bit type and we need to
> > explicitly declare a 32-bit type for the compatibility interface. From
> > sys/stat.h:
> > # ifndef __ino_t_defined
> > # ifndef __USE_FILE_OFFSET64
> > typedef __ino_t ino_t;
> > # else
> > typedef __ino64_t ino_t;
> > # endif
> > # define __ino_t_defined
> > # endif
> But isn't this the identical logic as for libselinux_ino_t?
> If _FILE_OFFSET_BITS is defined to be 64 libselinux_ino_t is
> typedef'ed to uint64_t and ino_t should also be a 64-bit integer.
> If _FILE_OFFSET_BITS is not 64 libselinux_ino_t is typedef'ed to
> uint32_t and ino_t should also be a 32-bit integer.
You're right, I overlooked this when refactoring based on Kees's feedback in
<https://lore.kernel.org/selinux/Zdrh%2FeuXdvdWlVSp@xxxxxxxxxxxxxxx/T/#m1d767f13e043e662555f6b8d8ddbffe033435d33>.
We want the entry point exposed to the caller to always be the one using the
same ino_t size as the rest of the calling code. So there's no need for
this extra typedef; fixed.
> > > > > diff --git a/libselinux/src/Makefile b/libselinux/src/Makefile
> > > > > index d3b981fc..267291aa 100644
> > > > > --- a/libselinux/src/Makefile
> > > > > +++ b/libselinux/src/Makefile
> > > > > @@ -87,6 +87,7 @@ CFLAGS ?= -O -Wall -W -Wundef -Wformat-y2k -Wformat-security -Winit-self -Wmissi
> > > > > -fstack-protector-all --param=ssp-buffer-size=4 -fexceptions \
> > > > > -fasynchronous-unwind-tables -fdiagnostics-show-option \
> > > > > -Werror -Wno-aggregate-return \
> > > > > + -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 \
> > > This won't work if CFLAGS are customized during build (e.g. by dpkg).
> > > Also utils/ is unaffected.
> > > Maybe use something like:
> > > libselinux/Makefile:
> > > USE_LFS ?= y
> > > export USE_LFS
> > > libselinux/{src,utils}/Makefile:
> > > ifeq ($(USE_LFS),y)
> > > override CFLAGS += -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64
> > > endif
> > Thanks, I'm happy to amend the patch to do that (but will wait to converge
> > on the other points above before I resubmit).
As an aside here, it doesn't actually matter if the utils are built with LFS
support for this purpose; the point is to make sure the library isn't broken
for callers, whether they have LFS enabled or not. But as long as we're
changing the library anyway to always be LFS-compatible, there's no harm in
also turning it on for the utils.
Attached an updated patch which I think addresses all your feedback.
--
Steve Langasek Give me a lever long enough and a Free OS
Debian Developer to set it on, and I can move the world.
Ubuntu Developer https://www.debian.org/
slangasek@xxxxxxxxxx vorlon@xxxxxxxxxx
From fb2e5ecaa84a2bb3d9f1f3946968add62e0ce5df Mon Sep 17 00:00:00 2001
From: Steve Langasek <steve.langasek@xxxxxxxxxxxxx>
Date: Thu, 15 Feb 2024 15:22:45 -0800
Subject: [PATCH] Always build for LFS mode on 32-bit archs.
Maintains the type signature of the existing matchpathcon_filespec_add()
entry point on 32-bit archs but maps the API to a new
matchpathcon_filespec_add64() entry point that takes a 64-bit ino_t argument
instead.
Software on 32-bit Linux ports which historically use a 32-bit time_t (thus
affected by the y2038 problem) have, as a precondition of migrating to
64-bit time_t, that they also migrate to large filesystem support because
glibc does not provide entry points for the cross-product of
(LFS: yes, LFS: no) x (time_t: 32, time_t: 64).
In order to support smooth migration of such operating systems from 32-bit
time_t to 64-bit time_t, it is useful for libselinux to:
- provide entry points on 32-bit systems for both LFS and non-LFS variants
of the API (as glibc itself does)
- use LFS internally for all filesystem calls (just in case)
- map the API call to the correct implementation based on the build
environment of the caller.
Signed-off-by: Steve Langasek <steve.langasek@xxxxxxxxxxxxx>
---
libselinux/Makefile | 6 ++++++
libselinux/include/selinux/selinux.h | 5 +++++
libselinux/src/Makefile | 2 ++
libselinux/src/libselinux.map | 5 +++++
libselinux/src/matchpathcon.c | 16 ++++++++++++++++
libselinux/utils/Makefile | 2 ++
6 files changed, 36 insertions(+)
diff --git a/libselinux/Makefile b/libselinux/Makefile
index 6d9e2736..a50b6491 100644
--- a/libselinux/Makefile
+++ b/libselinux/Makefile
@@ -34,6 +34,12 @@ PCRE_CFLAGS += $(shell $(PKG_CONFIG) --cflags $(PCRE_MODULE))
PCRE_LDLIBS := $(shell $(PKG_CONFIG) --libs $(PCRE_MODULE))
export PCRE_MODULE PCRE_CFLAGS PCRE_LDLIBS
+USE_LFS ?= y
+ifeq ($(USE_LFS),y)
+ LFS_CFLAGS := -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64
+endif
+export LFS_CFLAGS
+
OS := $(shell uname)
export OS
diff --git a/libselinux/include/selinux/selinux.h b/libselinux/include/selinux/selinux.h
index a0948853..080b486c 100644
--- a/libselinux/include/selinux/selinux.h
+++ b/libselinux/include/selinux/selinux.h
@@ -1,8 +1,10 @@
#ifndef _SELINUX_H_
#define _SELINUX_H_
+#include <stdint.h>
#include <sys/types.h>
#include <stdarg.h>
+#include <asm/bitsperlong.h>
#ifdef __cplusplus
extern "C" {
@@ -521,6 +523,9 @@ extern int matchpathcon_index(const char *path,
with the same inode (e.g. due to multiple hard links). If so, then
use the latter of the two specifications based on their order in the
file contexts configuration. Return the used specification index. */
+#if defined(_FILE_OFFSET_BITS) && _FILE_OFFSET_BITS == 64 && __BITS_PER_LONG < 64
+#define matchpathcon_filespec_add matchpathcon_filespec_add64
+#endif
extern int matchpathcon_filespec_add(ino_t ino, int specind, const char *file);
/* Destroy any inode associations that have been added, e.g. to restart
diff --git a/libselinux/src/Makefile b/libselinux/src/Makefile
index d3b981fc..9580cce8 100644
--- a/libselinux/src/Makefile
+++ b/libselinux/src/Makefile
@@ -89,6 +89,8 @@ CFLAGS ?= -O -Wall -W -Wundef -Wformat-y2k -Wformat-security -Winit-self -Wmissi
-Werror -Wno-aggregate-return \
$(EXTRA_CFLAGS)
+override CFLAGS += $(LFS_CFLAGS)
+
LD_SONAME_FLAGS=-soname,$(LIBSO),--version-script=libselinux.map,-z,defs,-z,relro
ifeq ($(OS), Darwin)
diff --git a/libselinux/src/libselinux.map b/libselinux/src/libselinux.map
index 5e00f45b..5176c8a9 100644
--- a/libselinux/src/libselinux.map
+++ b/libselinux/src/libselinux.map
@@ -252,3 +252,8 @@ LIBSELINUX_3.5 {
getpidprevcon;
getpidprevcon_raw;
} LIBSELINUX_3.4;
+
+LIBSELINUX_3.6 {
+ global:
+ matchpathcon_filespec_add64;
+} LIBSELINUX_3.5;
diff --git a/libselinux/src/matchpathcon.c b/libselinux/src/matchpathcon.c
index e44734c3..f8ee4b4b 100644
--- a/libselinux/src/matchpathcon.c
+++ b/libselinux/src/matchpathcon.c
@@ -261,6 +261,22 @@ int matchpathcon_filespec_add(ino_t ino, int specind, const char *file)
return -1;
}
+#if _FILE_OFFSET_BITS == 64 && __BITS_PER_LONG < 64
+/* alias defined in the public header but we undefine it here */
+#undef matchpathcon_filespec_add
+
+/* ABI backwards-compatible shim for non-LFS 32-bit systems */
+
+extern int matchpathcon_filespec_add(unsigned long ino, int specind,
+ const char *file);
+
+int matchpathcon_filespec_add(unsigned long ino, int specind,
+ const char *file)
+{
+ return matchpathcon_filespec_add64(ino, specind, file);
+}
+#endif
+
/*
* Evaluate the association hash table distribution.
*/
diff --git a/libselinux/utils/Makefile b/libselinux/utils/Makefile
index f3cedc11..0d7095b1 100644
--- a/libselinux/utils/Makefile
+++ b/libselinux/utils/Makefile
@@ -36,6 +36,8 @@ CFLAGS ?= -O -Wall -W -Wundef -Wformat-y2k -Wformat-security -Winit-self -Wmissi
-Werror -Wno-aggregate-return -Wno-redundant-decls -Wstrict-overflow=5 \
$(EXTRA_CFLAGS)
+override CFLAGS += $(LFS_CFLAGS)
+
ifeq ($(OS), Darwin)
override CFLAGS += -I/opt/local/include -I../../libsepol/include
override LDFLAGS += -L../../libsepol/src -undefined dynamic_lookup
--
2.40.1
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