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Eliminate runtime function pointer mods in autotools checks
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PaX/GrSecurity patched kernels implement a dialect of C that relies on a
GCC plugin for enforcement. A basic idea in this dialect is that
function pointers in structures should not change during runtime.
This causes code that modifies function pointers at runtime to fail to
compile in many instances. The autotools checks rely on whether or
not small test cases compile against a given kernel. Some
autotools checks assume some default case if other cases fail. When one
of these autotools checks tests a PaX/GrSecurity patched kernel by
modifying a function pointer at runtime, the default case will be used.

Early detection of such situations is possible by relying on compiler
warnings, which are compiler errors when --enable-debug is used.
Unfortunately, very few people build ZFS with --enable-debug. The more
common situation is that these issues manifest themselves as runtime
failures in the form of NULL pointer exceptions.

Previous patches that addressed such issues with PaX/GrSecurity
compatibility largely relied on rewriting autotools checks to avoid
runtime function pointer modification or the addition of PaX/GrSecurity
specific checks. This patch takes the previous work to its logical
conclusion by eliminating the use of runtime function pointer
modification. This permits the removal of PaX-specific autotools checks
in favor of ones that work across all supported kernels.

This should resolve issues that were reported to occur with
PaX/GrSecurity-patched Linux 3.7.5 kernels on Gentoo Linux.

https://bugs.gentoo.org/show_bug.cgi?id=457176

We should be able to prevent future regressions in PaX/GrSecurity
compatibility by ensuring that all changes to ZFSOnLinux avoid runtime
function pointer modification. At the same time, this does not solve the
issue of silent failures triggering default cases in the autotools
check, which is what permitted these regressions to become runtime
failures in the first place. This will need to be addressed in a future
patch.

Reported-by: Marcin Mirosław <bug@mejor.pl>
Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1300
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@ryao @behlendorf
ryao authored and behlendorf committed Mar 4, 2013
1 parent 8128bd8 commit c38367c
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Showing 10 changed files with 113 additions and 150 deletions.
25 changes: 12 additions & 13 deletions config/kernel-bdev-block-device-operations.m4
View file
Expand Up @@ -7,24 +7,23 @@ AC_DEFUN([ZFS_AC_KERNEL_BDEV_BLOCK_DEVICE_OPERATIONS], [
EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
ZFS_LINUX_TRY_COMPILE([
#include <linux/blkdev.h>
],[
int (*blk_open) (struct block_device *, fmode_t) = NULL;
int (*blk_release) (struct gendisk *, fmode_t) = NULL;
int (*blk_ioctl) (struct block_device *, fmode_t,
unsigned, unsigned long) = NULL;
int (*blk_compat_ioctl) (struct block_device *, fmode_t,
unsigned, unsigned long) = NULL;
struct block_device_operations blk_ops = {
int blk_open(struct block_device *bdev, fmode_t mode)
{ return 0; }
int blk_release(struct gendisk *g, fmode_t mode) { return 0; }
int blk_ioctl(struct block_device *bdev, fmode_t mode,
unsigned x, unsigned long y) { return 0; }
int blk_compat_ioctl(struct block_device * bdev, fmode_t mode,
unsigned x, unsigned long y) { return 0; }
static const struct block_device_operations
bops __attribute__ ((unused)) = {
.open = blk_open,
.release = blk_release,
.ioctl = blk_ioctl,
.compat_ioctl = blk_compat_ioctl,
};
blk_ops.open(NULL, 0);
blk_ops.release(NULL, 0);
blk_ops.ioctl(NULL, 0, 0, 0);
blk_ops.compat_ioctl(NULL, 0, 0, 0);
],[
],[
AC_MSG_RESULT(struct block_device)
AC_DEFINE(HAVE_BDEV_BLOCK_DEVICE_OPERATIONS, 1,
Expand Down
8 changes: 4 additions & 4 deletions config/kernel-bio-end-io-t-args.m4
View file
Expand Up @@ -11,11 +11,11 @@ AC_DEFUN([ZFS_AC_KERNEL_BIO_END_IO_T_ARGS], [
AC_MSG_CHECKING([whether bio_end_io_t wants 2 args])
ZFS_LINUX_TRY_COMPILE([
#include <linux/bio.h>
],[
void (*wanted_end_io)(struct bio *, int) = NULL;
bio_end_io_t *local_end_io __attribute__ ((unused));
local_end_io = wanted_end_io;
void wanted_end_io(struct bio *bio, int x) { return; }
bio_end_io_t *end_io __attribute__ ((unused)) = wanted_end_io;
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_2ARGS_BIO_END_IO_T, 1,
Expand Down
15 changes: 9 additions & 6 deletions config/kernel-create-nameidata.m4
View file
Expand Up @@ -5,17 +5,20 @@ AC_DEFUN([ZFS_AC_KERNEL_CREATE_NAMEIDATA], [
AC_MSG_CHECKING([whether iops->create() takes struct nameidata])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
#ifdef HAVE_MKDIR_UMODE_T
int (*inode_create) (struct inode *,struct dentry *,
umode_t, struct nameidata *) = NULL;
int inode_create(struct inode *inode ,struct dentry *dentry,
umode_t umode, struct nameidata *nidata) { return 0; }
#else
int (*inode_create) (struct inode *,struct dentry *,
int, struct nameidata *) = NULL;
int inode_create(struct inode *inode,struct dentry *dentry,
int umode, struct nameidata * nidata) { return 0; }
#endif
struct inode_operations iops __attribute__ ((unused)) = {
static const struct inode_operations
iops __attribute__ ((unused)) = {
.create = inode_create,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_CREATE_NAMEIDATA, 1,
Expand Down
12 changes: 8 additions & 4 deletions config/kernel-dentry-operations.m4
View file
Expand Up @@ -5,11 +5,15 @@ AC_DEFUN([ZFS_AC_KERNEL_D_REVALIDATE_NAMEIDATA], [
AC_MSG_CHECKING([whether dops->d_revalidate() takes struct nameidata])
ZFS_LINUX_TRY_COMPILE([
#include <linux/dcache.h>
],[
int (*revalidate) (struct dentry *, struct nameidata *) = NULL;
struct dentry_operations dops __attribute__ ((unused)) = {
.d_revalidate = revalidate,
int revalidate (struct dentry *dentry,
struct nameidata *nidata) { return 0; }
static const struct dentry_operations
dops __attribute__ ((unused)) = {
.d_revalidate = revalidate,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_D_REVALIDATE_NAMEIDATA, 1,
Expand Down
11 changes: 7 additions & 4 deletions config/kernel-dirty-inode.m4
View file
Expand Up @@ -8,11 +8,14 @@ AC_DEFUN([ZFS_AC_KERNEL_DIRTY_INODE_WITH_FLAGS], [
AC_MSG_CHECKING([whether sops->dirty_inode() wants flags])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
void (*dirty_inode) (struct inode *, int) = NULL;
struct super_operations sops __attribute__ ((unused));
sops.dirty_inode = dirty_inode;
void dirty_inode(struct inode *a, int b) { return; }
static const struct super_operations
sops __attribute__ ((unused)) = {
.dirty_inode = dirty_inode,
};
],[
],[
AC_MSG_RESULT([yes])
AC_DEFINE(HAVE_DIRTY_INODE_WITH_FLAGS, 1,
Expand Down
45 changes: 16 additions & 29 deletions config/kernel-fallocate.m4
View file
Expand Up @@ -5,11 +5,15 @@ AC_DEFUN([ZFS_AC_KERNEL_FILE_FALLOCATE], [
AC_MSG_CHECKING([whether fops->fallocate() exists])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
long (*fallocate) (struct file *, int, loff_t, loff_t) = NULL;
struct file_operations fops __attribute__ ((unused)) = {
.fallocate = fallocate,
long test_fallocate(struct file *file, int mode,
loff_t offset, loff_t len) { return 0; }
static const struct file_operations
fops __attribute__ ((unused)) = {
.fallocate = test_fallocate,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_FILE_FALLOCATE, 1, [fops->fallocate() exists])
Expand All @@ -25,34 +29,18 @@ AC_DEFUN([ZFS_AC_KERNEL_INODE_FALLOCATE], [
AC_MSG_CHECKING([whether iops->fallocate() exists])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
long (*fallocate) (struct inode *, int, loff_t, loff_t) = NULL;
struct inode_operations fops __attribute__ ((unused)) = {
.fallocate = fallocate,
};
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_INODE_FALLOCATE, 1, [fops->fallocate() exists])
],[
AC_MSG_RESULT(no)
])
])
dnl #
dnl # PaX Linux 2.6.38 - 3.x API
dnl #
AC_DEFUN([ZFS_AC_PAX_KERNEL_FILE_FALLOCATE], [
AC_MSG_CHECKING([whether fops->fallocate() exists])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
long (*fallocate) (struct file *, int, loff_t, loff_t) = NULL;
struct file_operations_no_const fops __attribute__ ((unused)) = {
.fallocate = fallocate,
long test_fallocate(struct inode *inode, int mode,
loff_t offset, loff_t len) { return 0; }
static const struct inode_operations
fops __attribute__ ((unused)) = {
.fallocate = test_fallocate,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_FILE_FALLOCATE, 1, [fops->fallocate() exists])
AC_DEFINE(HAVE_INODE_FALLOCATE, 1, [fops->fallocate() exists])
],[
AC_MSG_RESULT(no)
])
Expand All @@ -65,5 +53,4 @@ dnl #
AC_DEFUN([ZFS_AC_KERNEL_FALLOCATE], [
ZFS_AC_KERNEL_FILE_FALLOCATE
ZFS_AC_KERNEL_INODE_FALLOCATE
ZFS_AC_PAX_KERNEL_FILE_FALLOCATE
])
91 changes: 21 additions & 70 deletions config/kernel-fsync.m4
View file
Expand Up @@ -4,11 +4,15 @@ dnl #
AC_DEFUN([ZFS_AC_KERNEL_FSYNC_WITH_DENTRY], [
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
int (*fsync) (struct file *, struct dentry *, int) = NULL;
struct file_operations fops __attribute__ ((unused));
fops.fsync = fsync;
int test_fsync(struct file *f, struct dentry *dentry, int x)
{ return 0; }
static const struct file_operations
fops __attribute__ ((unused)) = {
.fsync = test_fsync,
};
],[
],[
AC_MSG_RESULT([dentry])
AC_DEFINE(HAVE_FSYNC_WITH_DENTRY, 1,
Expand All @@ -23,11 +27,14 @@ dnl #
AC_DEFUN([ZFS_AC_KERNEL_FSYNC_WITHOUT_DENTRY], [
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
int (*fsync) (struct file *, int) = NULL;
struct file_operations fops __attribute__ ((unused));
fops.fsync = fsync;
int test_fsync(struct file *f, int x) { return 0; }
static const struct file_operations
fops __attribute__ ((unused)) = {
.fsync = test_fsync,
};
],[
],[
AC_MSG_RESULT([no dentry])
AC_DEFINE(HAVE_FSYNC_WITHOUT_DENTRY, 1,
Expand All @@ -42,68 +49,15 @@ dnl #
AC_DEFUN([ZFS_AC_KERNEL_FSYNC_RANGE], [
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
int (*fsync) (struct file *, loff_t, loff_t, int) = NULL;
struct file_operations fops __attribute__ ((unused));
fops.fsync = fsync;
],[
AC_MSG_RESULT([range])
AC_DEFINE(HAVE_FSYNC_RANGE, 1,
[fops->fsync() with range])
],[
])
])
dnl #
dnl # PaX Linux 2.6.x - 2.6.34 API
dnl #
AC_DEFUN([ZFS_AC_PAX_KERNEL_FSYNC_WITH_DENTRY], [
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
int (*fsync) (struct file *, struct dentry *, int) = NULL;
file_operations_no_const fops __attribute__ ((unused));
int test_fsync(struct file *f, loff_t a, loff_t b, int c)
{ return 0; }
fops.fsync = fsync;
],[
AC_MSG_RESULT([dentry])
AC_DEFINE(HAVE_FSYNC_WITH_DENTRY, 1,
[fops->fsync() with dentry])
static const struct file_operations
fops __attribute__ ((unused)) = {
.fsync = test_fsync,
};
],[
])
])

dnl #
dnl # PaX Linux 2.6.35 - Linux 3.0 API
dnl #
AC_DEFUN([ZFS_AC_PAX_KERNEL_FSYNC_WITHOUT_DENTRY], [
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
int (*fsync) (struct file *, int) = NULL;
file_operations_no_const fops __attribute__ ((unused));
fops.fsync = fsync;
],[
AC_MSG_RESULT([no dentry])
AC_DEFINE(HAVE_FSYNC_WITHOUT_DENTRY, 1,
[fops->fsync() without dentry])
],[
])
])

dnl #
dnl # PaX Linux 3.1 - 3.x API
dnl #
AC_DEFUN([ZFS_AC_PAX_KERNEL_FSYNC_RANGE], [
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
int (*fsync) (struct file *, loff_t, loff_t, int) = NULL;
file_operations_no_const fops __attribute__ ((unused));
fops.fsync = fsync;
],[
AC_MSG_RESULT([range])
AC_DEFINE(HAVE_FSYNC_RANGE, 1,
Expand All @@ -117,7 +71,4 @@ AC_DEFUN([ZFS_AC_KERNEL_FSYNC], [
ZFS_AC_KERNEL_FSYNC_WITH_DENTRY
ZFS_AC_KERNEL_FSYNC_WITHOUT_DENTRY
ZFS_AC_KERNEL_FSYNC_RANGE
ZFS_AC_PAX_KERNEL_FSYNC_WITH_DENTRY
ZFS_AC_PAX_KERNEL_FSYNC_WITHOUT_DENTRY
ZFS_AC_PAX_KERNEL_FSYNC_RANGE
])
14 changes: 9 additions & 5 deletions config/kernel-lookup-nameidata.m4
View file
Expand Up @@ -5,12 +5,16 @@ AC_DEFUN([ZFS_AC_KERNEL_LOOKUP_NAMEIDATA], [
AC_MSG_CHECKING([whether iops->lookup() takes struct nameidata])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
struct dentry * (*inode_lookup) (struct inode *,struct dentry *,
struct nameidata *) = NULL;
struct inode_operations iops __attribute__ ((unused)) = {
.lookup = inode_lookup,
struct dentry *inode_lookup(struct inode *inode,
struct dentry *dentry, struct nameidata *nidata)
{ return NULL; }
static const struct inode_operations iops
__attribute__ ((unused)) = {
.lookup = inode_lookup,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_LOOKUP_NAMEIDATA, 1,
Expand Down
10 changes: 7 additions & 3 deletions config/kernel-mkdir-umode-t.m4
View file
Expand Up @@ -10,11 +10,15 @@ AC_DEFUN([ZFS_AC_KERNEL_MKDIR_UMODE_T], [
AC_MSG_CHECKING([whether iops->create()/mkdir()/mknod() take umode_t])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
int (*mkdir) (struct inode *,struct dentry *,umode_t) = NULL;
struct inode_operations iops __attribute__ ((unused)) = {
int mkdir(struct inode *inode, struct dentry *dentry,
umode_t umode) { return 0; }
static const struct inode_operations
iops __attribute__ ((unused)) = {
.mkdir = mkdir,
};
],[
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_MKDIR_UMODE_T, 1,
Expand Down

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