[PATCH 0/5] mm: clarify nofail memory allocation

[Barry Song <21cnbao@gmail.com>]

From: Barry Song <v-songbaohua@oppo.com>

__GFP_NOFAIL carries the semantics of never failing, so its callers
do not check the return value:
  %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller
  cannot handle allocation failures. The allocation could block
  indefinitely but will never return with failure. Testing for
  failure is pointless.

However, __GFP_NOFAIL can sometimes fail if it exceeds size limits
or is used with GFP_ATOMIC/GFP_NOWAIT in a non-sleepable context.
This can expose security vulnerabilities due to potential NULL
dereferences.

Since __GFP_NOFAIL does not support non-blocking allocation, we introduce
GFP_NOFAIL with inclusive blocking semantics and encourage using GFP_NOFAIL
as a replacement for __GFP_NOFAIL in non-mm.

If we must still fail a nofail allocation, we should trigger a BUG rather
than exposing NULL dereferences to callers who do not check the return
value.

* The discussion started from this topic:
 [PATCH RFC] mm: warn potential return NULL for kmalloc_array and
             kvmalloc_array with __GFP_NOFAIL

 https://lore.kernel.org/linux-mm/20240717230025.77361-1-21cnbao@gmail.com/

Thank you to Michal, Christoph, Vlastimil, and Hailong for all the
comments.

Barry Song (5):
  vpda: try to fix the potential crash due to misusing __GFP_NOFAIL
  mm: Document __GFP_NOFAIL must be blockable
  mm: BUG_ON to avoid NULL deference while __GFP_NOFAIL fails
  mm: Introduce GFP_NOFAIL with the inclusion of __GFP_RECLAIM
  non-mm: discourage the usage of __GFP_NOFAIL and encourage GFP_NOFAIL

 arch/powerpc/sysdev/xive/common.c             |  2 +-
 drivers/gpu/drm/drm_modeset_lock.c            |  2 +-
 drivers/gpu/drm/nouveau/nouveau_dmem.c        |  8 +++----
 drivers/gpu/drm/virtio/virtgpu_vq.c           |  2 +-
 drivers/hv/vmbus_drv.c                        |  2 +-
 drivers/infiniband/hw/cxgb4/mem.c             |  4 ++--
 drivers/md/dm-region-hash.c                   |  2 +-
 .../chelsio/inline_crypto/chtls/chtls_cm.c    |  6 ++---
 .../chelsio/inline_crypto/chtls/chtls_hw.c    |  2 +-
 drivers/target/iscsi/cxgbit/cxgbit_cm.c       |  2 +-
 drivers/tty/tty_ldisc.c                       |  2 +-
 drivers/vdpa/vdpa_user/iova_domain.c          | 24 +++++++++++++++----
 fs/bcachefs/btree_iter.c                      |  2 +-
 fs/bcachefs/fs-io-buffered.c                  |  2 +-
 fs/bcachefs/io_write.c                        |  2 +-
 fs/btrfs/extent_io.c                          |  8 +++----
 fs/buffer.c                                   |  6 ++---
 fs/erofs/fscache.c                            |  2 +-
 fs/erofs/zdata.c                              | 10 ++++----
 fs/ext4/extents.c                             |  8 +++----
 fs/ext4/extents_status.c                      |  4 ++--
 fs/ext4/mballoc.c                             | 12 +++++-----
 fs/ext4/page-io.c                             |  2 +-
 fs/f2fs/checkpoint.c                          |  2 +-
 fs/f2fs/data.c                                |  4 ++--
 fs/f2fs/f2fs.h                                |  2 +-
 fs/f2fs/node.c                                |  2 +-
 fs/fuse/dev.c                                 |  2 +-
 fs/fuse/file.c                                |  4 ++--
 fs/fuse/inode.c                               |  4 ++--
 fs/fuse/virtio_fs.c                           |  4 ++--
 fs/gfs2/meta_io.c                             |  2 +-
 fs/gfs2/rgrp.c                                |  6 ++---
 fs/gfs2/trans.c                               |  2 +-
 fs/iomap/buffered-io.c                        |  2 +-
 fs/jbd2/journal.c                             |  4 ++--
 fs/jbd2/revoke.c                              |  2 +-
 fs/jbd2/transaction.c                         |  6 ++---
 fs/notify/fanotify/fanotify.c                 |  2 +-
 fs/reiserfs/journal.c                         |  2 +-
 fs/udf/directory.c                            |  2 +-
 fs/xfs/libxfs/xfs_alloc.c                     |  2 +-
 fs/xfs/libxfs/xfs_attr_leaf.c                 |  8 +++----
 fs/xfs/libxfs/xfs_bmap.c                      |  2 +-
 fs/xfs/libxfs/xfs_btree.h                     |  2 +-
 fs/xfs/libxfs/xfs_btree_staging.c             |  2 +-
 fs/xfs/libxfs/xfs_da_btree.c                  |  8 +++----
 fs/xfs/libxfs/xfs_defer.c                     |  4 ++--
 fs/xfs/libxfs/xfs_dir2.c                      | 10 ++++----
 fs/xfs/libxfs/xfs_dir2_block.c                |  2 +-
 fs/xfs/libxfs/xfs_dir2_sf.c                   |  8 +++----
 fs/xfs/libxfs/xfs_exchmaps.c                  |  4 ++--
 fs/xfs/libxfs/xfs_iext_tree.c                 |  4 ++--
 fs/xfs/libxfs/xfs_inode_fork.c                | 14 +++++------
 fs/xfs/libxfs/xfs_refcount.c                  |  4 ++--
 fs/xfs/libxfs/xfs_rmap.c                      |  2 +-
 fs/xfs/xfs_attr_item.c                        |  8 +++----
 fs/xfs/xfs_attr_list.c                        |  2 +-
 fs/xfs/xfs_bmap_item.c                        |  6 ++---
 fs/xfs/xfs_buf.c                              |  8 +++----
 fs/xfs/xfs_buf_item.c                         |  4 ++--
 fs/xfs/xfs_buf_item_recover.c                 |  2 +-
 fs/xfs/xfs_dquot.c                            |  2 +-
 fs/xfs/xfs_exchmaps_item.c                    |  4 ++--
 fs/xfs/xfs_extent_busy.c                      |  2 +-
 fs/xfs/xfs_extfree_item.c                     | 10 ++++----
 fs/xfs/xfs_icache.c                           |  2 +-
 fs/xfs/xfs_icreate_item.c                     |  2 +-
 fs/xfs/xfs_inode_item.c                       |  2 +-
 fs/xfs/xfs_inode_item_recover.c               |  2 +-
 fs/xfs/xfs_iunlink_item.c                     |  2 +-
 fs/xfs/xfs_iwalk.c                            |  2 +-
 fs/xfs/xfs_log.c                              |  2 +-
 fs/xfs/xfs_log_cil.c                          |  2 +-
 fs/xfs/xfs_log_recover.c                      |  6 ++---
 fs/xfs/xfs_mount.c                            |  2 +-
 fs/xfs/xfs_mru_cache.c                        |  4 ++--
 fs/xfs/xfs_qm.c                               |  4 ++--
 fs/xfs/xfs_refcount_item.c                    |  8 +++----
 fs/xfs/xfs_rmap_item.c                        |  8 +++----
 fs/xfs/xfs_rtalloc.c                          |  2 +-
 fs/xfs/xfs_super.c                            |  2 +-
 fs/xfs/xfs_trans.c                            |  4 ++--
 fs/xfs/xfs_trans_dquot.c                      |  2 +-
 include/linux/buffer_head.h                   |  4 ++--
 include/linux/gfp_types.h                     |  7 ++++++
 include/linux/slab.h                          |  4 +++-
 kernel/resource.c                             |  2 +-
 lib/list-test.c                               |  8 +++----
 lib/ref_tracker.c                             |  2 +-
 lib/rhashtable.c                              |  6 ++---
 lib/test_hmm.c                                |  6 ++---
 mm/page_alloc.c                               | 10 ++++----
 mm/util.c                                     |  1 +
 net/ceph/osd_client.c                         |  2 +-
 net/ceph/osdmap.c                             |  4 ++--
 net/core/sock.c                               |  4 ++--
 net/ipv4/inet_connection_sock.c               |  2 +-
 net/ipv4/tcp_output.c                         |  2 +-
 security/smack/smackfs.c                      |  2 +-
 100 files changed, 222 insertions(+), 196 deletions(-)

-- 
2.34.1