Fix 32-bit compat_sys_mmap() mapping VMA over 4Gb in 64-bit binaries
and 64-bit sys_mmap() mapping VMA only under 4Gb in 32-bit binaries.
Introduced new bases for compat syscalls in mm_struct:
mmap_compat_base and mmap_compat_legacy_base for top-down and
bottom-up allocations accordingly.
Taught arch_get_unmapped_area{,_topdown}() to use the new mmap_bases
in compat syscalls for high/low limits in vm_unmapped_area().
I discovered that bug on ZDTM tests for compat 32-bit C/R.
Working compat sys_mmap() in 64-bit binaries is really needed for that
purpose, as 32-bit applications are restored from 64-bit CRIU binary.
Signed-off-by: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx>
---
arch/Kconfig | 7 +++++++
arch/x86/Kconfig | 1 +
arch/x86/kernel/sys_x86_64.c | 28 ++++++++++++++++++++++++----
arch/x86/mm/mmap.c | 36 ++++++++++++++++++++++++------------
include/linux/mm_types.h | 5 +++++
5 files changed, 61 insertions(+), 16 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 99839c23d453..6bdca6d86855 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -671,6 +671,13 @@ config ARCH_MMAP_RND_COMPAT_BITS
This value can be changed after boot using the
/proc/sys/vm/mmap_rnd_compat_bits tunable
+config HAVE_ARCH_COMPAT_MMAP_BASES
+ bool
+ help
+ If this is set, one program can do native and compatible syscall
+ mmap() on architecture. Thus kernel has different bases to
+ compute high and low virtual address limits for allocation.
+
config HAVE_COPY_THREAD_TLS
bool
help
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e487493bbd47..b3acb836567a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -102,6 +102,7 @@ config X86
select HAVE_ARCH_KMEMCHECK
select HAVE_ARCH_MMAP_RND_BITS if MMU
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
+ select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index a55ed63b9f91..90be0839441d 100644
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -16,6 +16,7 @@
#include <linux/uaccess.h>
#include <linux/elf.h>
+#include <asm/compat.h>
#include <asm/ia32.h>
#include <asm/syscalls.h>
@@ -113,10 +114,19 @@ static void find_start_end(unsigned long flags, unsigned long *begin,
if (current->flags & PF_RANDOMIZE) {
*begin = randomize_page(*begin, 0x02000000);
}
- } else {
- *begin = current->mm->mmap_legacy_base;
- *end = TASK_SIZE;
+ return;
}
+
+#ifdef CONFIG_COMPAT
+ if (in_compat_syscall()) {
+ *begin = current->mm->mmap_compat_legacy_base;
+ *end = IA32_PAGE_OFFSET;
+ return;
+ }
+#endif
+
+ *begin = current->mm->mmap_legacy_base;
+ *end = TASK_SIZE_MAX;
}
unsigned long
@@ -157,6 +167,16 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
return vm_unmapped_area(&info);
}
+static unsigned long find_top(void)
+{
+#ifdef CONFIG_COMPAT
+ if (in_compat_syscall())
+ return current->mm->mmap_compat_base;
+ else
+#endif
+ return current->mm->mmap_base;
+}
+
unsigned long
arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
const unsigned long len, const unsigned long pgoff,
@@ -190,7 +210,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.length = len;
info.low_limit = PAGE_SIZE;
- info.high_limit = mm->mmap_base;
+ info.high_limit = find_top();
info.align_mask = 0;
info.align_offset = pgoff << PAGE_SHIFT;
if (filp) {
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 98be520fd270..99e6a81d9c87 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -70,6 +70,8 @@ static int mmap_is_legacy(void)
#ifdef CONFIG_COMPAT
static unsigned long arch_compat_rnd(void)
{
+ if (!(current->flags & PF_RANDOMIZE))
+ return 0;
return (get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1))
<< PAGE_SHIFT;
}
@@ -77,6 +79,8 @@ static unsigned long arch_compat_rnd(void)
static unsigned long arch_native_rnd(void)
{
+ if (!(current->flags & PF_RANDOMIZE))
+ return 0;
return (get_random_long() & ((1UL << mmap_rnd_bits) - 1)) << PAGE_SHIFT;
}
@@ -112,22 +116,30 @@ static unsigned long mmap_legacy_base(unsigned long rnd,
* This function, called very early during the creation of a new
* process VM image, sets up which VM layout function to use:
*/
-void arch_pick_mmap_layout(struct mm_struct *mm)
+static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
+ unsigned long random_factor, unsigned long task_size)
{
- unsigned long random_factor = 0UL;
-
- if (current->flags & PF_RANDOMIZE)
- random_factor = arch_mmap_rnd();
-
- mm->mmap_legacy_base = mmap_legacy_base(random_factor, TASK_SIZE);
+ *legacy_base = mmap_legacy_base(random_factor, task_size);
+ if (mmap_is_legacy())
+ *base = *legacy_base;
+ else
+ *base = mmap_base(random_factor, task_size);
+}
- if (mmap_is_legacy()) {
- mm->mmap_base = mm->mmap_legacy_base;
+void arch_pick_mmap_layout(struct mm_struct *mm)
+{
+ if (mmap_is_legacy())
mm->get_unmapped_area = arch_get_unmapped_area;
- } else {
- mm->mmap_base = mmap_base(random_factor, TASK_SIZE);
+ else
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
- }
+
+ arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
+ arch_native_rnd(), TASK_SIZE_MAX);
+
+#ifdef CONFIG_COMPAT
+ arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base,
+ arch_compat_rnd(), IA32_PAGE_OFFSET);
+#endif
}
const char *arch_vma_name(struct vm_area_struct *vma)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 808751d7b737..48274a84cebe 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -404,6 +404,11 @@ struct mm_struct {
#endif
unsigned long mmap_base; /* base of mmap area */
unsigned long mmap_legacy_base; /* base of mmap area in bottom-up allocations */
+#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
+ /* Base adresses for compatible mmap() */
+ unsigned long mmap_compat_base;
+ unsigned long mmap_compat_legacy_base;
+#endif
unsigned long task_size; /* size of task vm space */
unsigned long highest_vm_end; /* highest vma end address */
pgd_t * pgd;
--
2.11.0
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
