[PATCH v3 1/3] x86: process: Unify 32-bit and 64-bit copy_thread I/O bitmap handling

Josh Triplett
2014-10-29T16:02:57Z

The 32-bit and 64-bit versions of copy_thread have functionally
identical handling for copying the I/O bitmap, modulo differences in
error handling. Clean up the error paths in both by moving the copy of
the I/O bitmap to the end, to eliminate the need to free it if
subsequent copy steps fail; move the resulting identical code to a
static inline in a common header.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Kees Cook <keescook@chromium.org>
---
v3: No changes in this patch, only in patch 3/3.

arch/x86/kernel/process-io.h | 22 ++++++++++++++++++++++
arch/x86/kernel/process_32.c | 28 ++++++++--------------------
arch/x86/kernel/process_64.c | 25 +++++--------------------
3 files changed, 35 insertions(+), 40 deletions(-)
create mode 100644 arch/x86/kernel/process-io.h

diff --git a/arch/x86/kernel/process-io.h b/arch/x86/kernel/process-io.h
new file mode 100644
index 0000000..d884444
--- /dev/null
+++ b/arch/x86/kernel/process-io.h
@@ -0,0 +1,22 @@
+#ifndef _X86_KERNEL_PROCESS_IO_H
+#define _X86_KERNEL_PROCESS_IO_H
+
+static inline int copy_io_bitmap(struct task_struct *me,
+ struct task_struct *p)
+{
+ if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
+ p->thread.io_bitmap_ptr = kmemdup(me->thread.io_bitmap_ptr,
+ IO_BITMAP_BYTES, GFP_KERNEL);
+ if (!p->thread.io_bitmap_ptr) {
+ p->thread.io_bitmap_max = 0;
+ return -ENOMEM;
+ }
+ set_tsk_thread_flag(p, TIF_IO_BITMAP);
+ } else {
+ p->thread.io_bitmap_ptr = NULL;
+ }
+
+ return 0;
+}
+
+#endif /* _X86_KERNEL_PROCESS_IO_H */
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 8f3ebfe..07550ff 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -55,6 +55,8 @@
#include <asm/debugreg.h>
#include <asm/switch_to.h>

+#include "process-io.h"
+
asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");

@@ -134,7 +136,6 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
{
struct pt_regs *childregs = task_pt_regs(p);
struct task_struct *tsk;
- int err;

p->thread.sp = (unsigned long) childregs;
p->thread.sp0 = (unsigned long) (childregs+1);
@@ -166,32 +167,19 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,

p->thread.io_bitmap_ptr = NULL;
tsk = current;
- err = -ENOMEM;
-
- if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
- p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
- IO_BITMAP_BYTES, GFP_KERNEL);
- if (!p->thread.io_bitmap_ptr) {
- p->thread.io_bitmap_max = 0;
- return -ENOMEM;
- }
- set_tsk_thread_flag(p, TIF_IO_BITMAP);
- }
-
- err = 0;

/*
* Set a new TLS for the child thread?
*/
- if (clone_flags & CLONE_SETTLS)
+ if (clone_flags & CLONE_SETTLS) {
+ int err;
err = do_set_thread_area(p, -1,
(struct user_desc __user *)childregs->si, 0);
-
- if (err && p->thread.io_bitmap_ptr) {
- kfree(p->thread.io_bitmap_ptr);
- p->thread.io_bitmap_max = 0;
+ if(err)
+ return err;
}
- return err;
+
+ return copy_io_bitmap(tsk, p);
}

void
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 3ed4a68..b1babb4 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -50,6 +50,8 @@
#include <asm/debugreg.h>
#include <asm/switch_to.h>

+#include "process-io.h"
+
asmlinkage extern void ret_from_fork(void);

__visible DEFINE_PER_CPU(unsigned long, old_rsp);
@@ -154,7 +156,6 @@ static inline u32 read_32bit_tls(struct task_struct *t, int tls)
int copy_thread(unsigned long clone_flags, unsigned long sp,
unsigned long arg, struct task_struct *p)
{
- int err;
struct pt_regs *childregs;
struct task_struct *me = current;

@@ -191,21 +192,11 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
if (sp)
childregs->sp = sp;

- err = -ENOMEM;
- if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
- p->thread.io_bitmap_ptr = kmemdup(me->thread.io_bitmap_ptr,
- IO_BITMAP_BYTES, GFP_KERNEL);
- if (!p->thread.io_bitmap_ptr) {
- p->thread.io_bitmap_max = 0;
- return -ENOMEM;
- }
- set_tsk_thread_flag(p, TIF_IO_BITMAP);
- }
-
/*
* Set a new TLS for the child thread?
*/
if (clone_flags & CLONE_SETTLS) {
+ int err;
#ifdef CONFIG_IA32_EMULATION
if (test_thread_flag(TIF_IA32))
err = do_set_thread_area(p, -1,
@@ -214,16 +205,10 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
#endif
err = do_arch_prctl(p, ARCH_SET_FS, childregs->r8);
if (err)
- goto out;
- }
- err = 0;
-out:
- if (err && p->thread.io_bitmap_ptr) {
- kfree(p->thread.io_bitmap_ptr);
- p->thread.io_bitmap_max = 0;
+ return err;
}

- return err;
+ return copy_io_bitmap(me, p);
}

static void
--
2.1.1