2.4.17-pre8

 ipc

diff -Naur -X /home/marcelo/lib/dontdiff linux-2.4.16/ipc/shm.c linux/ipc/shm.c
--- linux-2.4.16/ipc/shm.c   Mon Nov 26 10:35:01 2001
+++ linux/ipc/shm.c   Sun Dec  9 18:07:37 2001
@@ -569,6 +569,7 @@
 {
    struct shmid_kernel *shp;
    unsigned long addr;
+   unsigned long size;
    struct file * file;
    int    err;
    unsigned long flags;
@@ -588,8 +589,12 @@
             return -EINVAL;
       }
       flags = MAP_SHARED | MAP_FIXED;
-   } else
+   } else {
+      if ((shmflg & SHM_REMAP))
+         return -EINVAL;
+
       flags = MAP_SHARED;
+   }
 
    if (shmflg & SHM_RDONLY) {
       prot = PROT_READ;
@@ -603,7 +608,7 @@
 
    /*
     * We cannot rely on the fs check since SYSV IPC does have an
-    * aditional creator id...
+    * additional creator id...
     */
    shp = shm_lock(shmid);
    if(shp == NULL)
@@ -618,11 +623,27 @@
       return -EACCES;
    }
    file = shp->shm_file;
+   size = file->f_dentry->d_inode->i_size;
    shp->shm_nattch++;
    shm_unlock(shmid);
 
    down_write(¤t->mm->mmap_sem);
-   user_addr = (void *) do_mmap (file, addr, file->f_dentry->d_inode->i_size, prot, flags, 0);
+   if (addr && !(shmflg & SHM_REMAP)) {
+      user_addr = ERR_PTR(-EINVAL);
+      if (find_vma_intersection(current->mm, addr, addr + size))
+         goto invalid;
+      /*
+       * If shm segment goes below stack, make sure there is some
+       * space left for the stack to grow (at least 4 pages).
+       */
+      if (addr < current->mm->start_stack &&
+          addr > current->mm->start_stack - size - PAGE_SIZE * 5)
+         goto invalid;
+   }
+      
+   user_addr = (void*) do_mmap (file, addr, size, prot, flags, 0);
+
+invalid:
    up_write(¤t->mm->mmap_sem);
 
    down (&shm_ids.sem);