[PATCH] x86_64: TASK_SIZE fixes for compatibility mode processes

Appended patch will setup compatibility mode TASK_SIZE properly.  This will
fix atleast three known bugs that can be encountered while running
compatibility mode apps.

a) A malicious 32bit app can have an elf section at 0xffffe000.  During
   exec of this app, we will have a memory leak as insert_vm_struct() is
   not checking for return value in syscall32_setup_pages() and thus not
   freeing the vma allocated for the vsyscall page.  And instead of exec
   failing (as it has addresses > TASK_SIZE), we were allowing it to
   succeed previously.

b) With a 32bit app, hugetlb_get_unmapped_area/arch_get_unmapped_area
   may return addresses beyond 32bits, ultimately causing corruption
   because of wrap-around and resulting in SEGFAULT, instead of returning
   ENOMEM.

c) 32bit app doing this below mmap will now fail.

  mmap((void *)(0xFFFFE000UL), 0x10000UL, PROT_READ|PROT_WRITE,
	MAP_FIXED|MAP_PRIVATE|MAP_ANON, 0, 0);

Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 7 deletions

diff --git a/arch/x86_64/kernel/ptrace.c b/arch/x86_64/kernel/ptrace.c
index 525f6a128a27..bbf64b59a21e 100644
--- a/arch/x86_64/kernel/ptrace.c
+++ b/arch/x86_64/kernel/ptrace.c
@@ -257,12 +257,12 @@ static int putreg(struct task_struct *child,
                         value &= 0xffff;
                         return 0;
                 case offsetof(struct user_regs_struct,fs_base):
-                        if (value >= TASK_SIZE)
+                        if (value >= TASK_SIZE_OF(child))
                                 return -EIO;
                         child->thread.fs = value;
                         return 0;
                 case offsetof(struct user_regs_struct,gs_base):
-                        if (value >= TASK_SIZE)
+                        if (value >= TASK_SIZE_OF(child))
                                 return -EIO;
                         child->thread.gs = value;
                         return 0;
@@ -279,7 +279,7 @@ static int putreg(struct task_struct *child,
                         break;
                 case offsetof(struct user_regs_struct, rip):
                         /* Check if the new RIP address is canonical */
-                        if (value >= TASK_SIZE)
+                        if (value >= TASK_SIZE_OF(child))
                                 return -EIO;
                         break;
         }
@@ -419,6 +419,8 @@ asmlinkage long sys_ptrace(long request, long pid, unsigned long addr, long data
                 break;
 
         case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
+        {
+                int dsize = test_tsk_thread_flag(child, TIF_IA32) ? 3 : 7;
                 ret = -EIO;
                 if ((addr & 7) ||
                     addr > sizeof(struct user) - 7)
@@ -430,22 +432,22 @@ asmlinkage long sys_ptrace(long request, long pid, unsigned long addr, long data
                         break;
                 /* Disallows to set a breakpoint into the vsyscall */
                 case offsetof(struct user, u_debugreg[0]):
-                        if (data >= TASK_SIZE-7) break;
+                        if (data >= TASK_SIZE_OF(child) - dsize) break;
                         child->thread.debugreg0 = data;
                         ret = 0;
                         break;
                 case offsetof(struct user, u_debugreg[1]):
-                        if (data >= TASK_SIZE-7) break;
+                        if (data >= TASK_SIZE_OF(child) - dsize) break;
                         child->thread.debugreg1 = data;
                         ret = 0;
                         break;
                 case offsetof(struct user, u_debugreg[2]):
-                        if (data >= TASK_SIZE-7) break;
+                        if (data >= TASK_SIZE_OF(child) - dsize) break;
                         child->thread.debugreg2 = data;
                         ret = 0;
                         break;
                 case offsetof(struct user, u_debugreg[3]):
-                        if (data >= TASK_SIZE-7) break;
+                        if (data >= TASK_SIZE_OF(child) - dsize) break;
                         child->thread.debugreg3 = data;
                         ret = 0;
                         break;
@@ -469,6 +471,7 @@ asmlinkage long sys_ptrace(long request, long pid, unsigned long addr, long data
                   break;
                 }
                 break;
+        }
         case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
         case PTRACE_CONT:    /* restart after signal. */