[Xen-devel] [PATCHv2 1/3] x86: process: Unify 32-bit and 64-bit copy_thread I/O bitmap handling

[Josh Triplett <josh@xxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
v2: Rebased and updated for changes to copy_thread; no other changes in
    patch 1/3.

 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 0de43e9..73a38c8 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);
@@ -168,34 +169,21 @@ int copy_thread(unsigned long clone_flags, unsigned long 
sp,
        p->thread.fpu_counter = 0;
        p->thread.io_bitmap_ptr = NULL;
        tsk = current;
-       err = -ENOMEM;
 
        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 
-       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 9c0280f..3b8f17c 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);
 
 asmlinkage 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;
 
@@ -192,23 +193,13 @@ int copy_thread(unsigned long clone_flags, unsigned long 
sp,
        if (sp)
                childregs->sp = sp;
 
-       err = -ENOMEM;
        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 
-       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,
@@ -217,16 +208,10 @@ 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
-- 
1.9.0


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