if (IS_ERR(shp))
return PTR_ERR(shp);
+ if (shp->shm_file != sfd->file) {
+ /* ID was reused */
+ shm_unlock(shp);
+ return -EINVAL;
+ }
+
shp->shm_atim = ktime_get_real_seconds();
shp->shm_lprid = task_tgid_vnr(current);
shp->shm_nattch++;
return sfd->vm_ops->fault(vmf);
}
+static int shm_split(struct vm_area_struct *vma, unsigned long addr)
+{
+ struct file *file = vma->vm_file;
+ struct shm_file_data *sfd = shm_file_data(file);
+
+ if (sfd->vm_ops && sfd->vm_ops->split)
+ return sfd->vm_ops->split(vma, addr);
+
+ return 0;
+}
+
#ifdef CONFIG_NUMA
static int shm_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
{
int ret;
/*
- * In case of remap_file_pages() emulation, the file can represent
- * removed IPC ID: propogate shm_lock() error to caller.
+ * In case of remap_file_pages() emulation, the file can represent an
+ * IPC ID that was removed, and possibly even reused by another shm
+ * segment already. Propagate this case as an error to caller.
*/
ret = __shm_open(vma);
if (ret)
struct shm_file_data *sfd = shm_file_data(file);
put_ipc_ns(sfd->ns);
+ fput(sfd->file);
shm_file_data(file) = NULL;
kfree(sfd);
return 0;
.open = shm_open, /* callback for a new vm-area open */
.close = shm_close, /* callback for when the vm-area is released */
.fault = shm_fault,
+ .split = shm_split,
#if defined(CONFIG_NUMA)
.set_policy = shm_set_policy,
.get_policy = shm_get_policy,
if (addr) {
if (addr & (shmlba - 1)) {
- /*
- * Round down to the nearest multiple of shmlba.
- * For sane do_mmap_pgoff() parameters, avoid
- * round downs that trigger nil-page and MAP_FIXED.
- */
- if ((shmflg & SHM_RND) && addr >= shmlba)
- addr &= ~(shmlba - 1);
- else
+ if (shmflg & SHM_RND) {
+ addr &= ~(shmlba - 1); /* round down */
+
+ /*
+ * Ensure that the round-down is non-nil
+ * when remapping. This can happen for
+ * cases when addr < shmlba.
+ */
+ if (!addr && (shmflg & SHM_REMAP))
+ goto out;
+ } else
#ifndef __ARCH_FORCE_SHMLBA
if (addr & ~PAGE_MASK)
#endif
file->f_mapping = shp->shm_file->f_mapping;
sfd->id = shp->shm_perm.id;
sfd->ns = get_ipc_ns(ns);
- sfd->file = shp->shm_file;
+ /*
+ * We need to take a reference to the real shm file to prevent the
+ * pointer from becoming stale in cases where the lifetime of the outer
+ * file extends beyond that of the shm segment. It's not usually
+ * possible, but it can happen during remap_file_pages() emulation as
+ * that unmaps the memory, then does ->mmap() via file reference only.
+ * We'll deny the ->mmap() if the shm segment was since removed, but to
+ * detect shm ID reuse we need to compare the file pointers.
+ */
+ sfd->file = get_file(shp->shm_file);
sfd->vm_ops = NULL;
err = security_mmap_file(file, prot, flags);