c/r: prctl: simplify PR_SET_MM on mm::code/data assignment

The mm::start_code, end_code, start_data, end_data members are set during
startup of executable file and are not changed after.

But the program itself might map new executable or/and data areas in time
so the original values written into mm fields mentioned above might not
have correspond VMA area at all, thus if one try to use this prctl codes
without underlied VMA, the error will be returned.

Drop this requirement.  This shrinks the code and eliminates redundant
calls to vma_flags_mismatch.  The worst thing one can do (if say to write
some bad values here) -- the weird results will be shown in
/proc/$pid/statm or in /proc/pid/stat.

Still, assignement of data on stack (such as command line and environment
variables) requires the underlied VMA to exist.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/sys.c b/kernel/sys.c
index bd214a6b7167644158ac2fcf095a041e730fd29f..66ca44c6875d8bc2ba8b4fd3aac04f72d96b5af3 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1727,42 +1727,21 @@ static int prctl_set_mm(int opt, unsigned long addr,
        if (addr >= TASK_SIZE)
                return -EINVAL;
 
-       error = -EINVAL;
-
        down_read(&mm->mmap_sem);
        vma = find_vma(mm, addr);
 
-       if (opt != PR_SET_MM_START_BRK &&
-           opt != PR_SET_MM_BRK &&
-           opt != PR_SET_MM_AUXV) {
-               /* It must be existing VMA */
-               if (!vma || vma->vm_start > addr)
-                       goto out;
-       }
-
        switch (opt) {
        case PR_SET_MM_START_CODE:
+               mm->start_code = addr;
+               break;
        case PR_SET_MM_END_CODE:
-               if (vma_flags_mismatch(vma, VM_READ | VM_EXEC,
-                                      VM_WRITE | VM_MAYSHARE))
-                       goto out;
-
-               if (opt == PR_SET_MM_START_CODE)
-                       mm->start_code = addr;
-               else
-                       mm->end_code = addr;
+               mm->end_code = addr;
                break;
-
        case PR_SET_MM_START_DATA:
+               mm->start_data = addr;
+               break;
        case PR_SET_MM_END_DATA:
-               if (vma_flags_mismatch(vma, VM_READ | VM_WRITE,
-                                      VM_EXEC | VM_MAYSHARE))
-                       goto out;
-
-               if (opt == PR_SET_MM_START_DATA)
-                       mm->start_data = addr;
-               else
-                       mm->end_data = addr;
+               mm->end_data = addr;
                break;
 
        case PR_SET_MM_START_BRK:
@@ -1801,6 +1780,8 @@ static int prctl_set_mm(int opt, unsigned long addr,
        case PR_SET_MM_ARG_END:
        case PR_SET_MM_ENV_START:
        case PR_SET_MM_ENV_END:
+               if (!vma)
+                       goto out;
 #ifdef CONFIG_STACK_GROWSUP
                if (vma_flags_mismatch(vma, VM_READ | VM_WRITE | VM_GROWSUP, 0))
 #else