kernel.git/fs/ext4/inode.c, branch linux-6.5.y

ext4: mark buffer new if it is unwritten to avoid stale data exposure

2023-11-28T17:15:16Z

commit 2cd8bdb5efc1e0d5b11a4b7ba6b922fd2736a87f upstream. ** Short Version ** In ext4 with dioread_nolock, we could have a scenario where the bh returned by get_blocks (ext4_get_block_unwritten()) in __block_write_begin_int() has UNWRITTEN and MAPPED flag set. Since such a bh does not have NEW flag set we never zero out the range of bh that is not under write, causing whatever stale data is present in the folio at that time to be written out to disk. To fix this mark the buffer as new, in case it is unwritten, in ext4_get_block_unwritten(). ** Long Version ** The issue mentioned above was resulting in two different bugs: 1. On block size < page size case in ext4, generic/269 was reliably failing with dioread_nolock. The state of the write was as follows: * The write was extending i_size. * The last block of the file was fallocated and had an unwritten extent * We were near ENOSPC and hence we were switching to non-delayed alloc allocation. In this case, the back trace that triggers the bug is as follows: ext4_da_write_begin() /* switch to nodelalloc due to low space */ ext4_write_begin() ext4_should_dioread_nolock() // true since mount flags still have delalloc __block_write_begin(..., ext4_get_block_unwritten) __block_write_begin_int() for(each buffer head in page) { /* first iteration, this is bh1 which contains i_size */ if (!buffer_mapped) get_block() /* returns bh with only UNWRITTEN and MAPPED */ /* second iteration, bh2 */ if (!buffer_mapped) get_block() /* we fail here, could be ENOSPC */ } if (err) /* * this would zero out all new buffers and mark them uptodate. * Since bh1 was never marked new, we skip it here which causes * the bug later. */ folio_zero_new_buffers(); /* ext4_wrte_begin() error handling */ ext4_truncate_failed_write() ext4_truncate() ext4_block_truncate_page() __ext4_block_zero_page_range() if(!buffer_uptodate()) ext4_read_bh_lock() ext4_read_bh() -> ... ext4_submit_bh_wbc() BUG_ON(buffer_unwritten(bh)); /* !!! */ 2. The second issue is stale data exposure with page size >= blocksize with dioread_nolock. The conditions needed for it to happen are same as the previous issue ie dioread_nolock around ENOSPC condition. The issue is also similar where in __block_write_begin_int() when we call ext4_get_block_unwritten() on the buffer_head and the underlying extent is unwritten, we get an unwritten and mapped buffer head. Since it is not new, we never zero out the partial range which is not under write, thus writing stale data to disk. This can be easily observed with the following reproducer: fallocate -l 4k testfile xfs_io -c "pwrite 2k 2k" testfile # hexdump output will have stale data in from byte 0 to 2k in testfile hexdump -C testfile NOTE: To trigger this, we need dioread_nolock enabled and write happening via ext4_write_begin(), which is usually used when we have -o nodealloc. Since dioread_nolock is disabled with nodelalloc, the only alternate way to call ext4_write_begin() is to ensure that delayed alloc switches to nodelalloc ie ext4_da_write_begin() calls ext4_write_begin(). This will usually happen when ext4 is almost full like the way generic/269 was triggering it in Issue 1 above. This might make the issue harder to hit. Hence, for reliable replication, I used the below patch to temporarily allow dioread_nolock with nodelalloc and then mount the disk with -o nodealloc,dioread_nolock. With this you can hit the stale data issue 100% of times: @@ -508,8 +508,8 @@ static inline int ext4_should_dioread_nolock(struct inode *inode) if (ext4_should_journal_data(inode)) return 0; /* temporary fix to prevent generic/422 test failures */ - if (!test_opt(inode->i_sb, DELALLOC)) - return 0; + // if (!test_opt(inode->i_sb, DELALLOC)) + // return 0; return 1; } After applying this patch to mark buffer as NEW, both the above issues are fixed. Signed-off-by: Ojaswin Mujoo Cc: stable@kernel.org Reviewed-by: Jan Kara Reviewed-by: "Ritesh Harjani (IBM)" Link: https://lore.kernel.org/r/d0ed09d70a9733fbb5349c5c7b125caac186ecdf.1695033645.git.ojaswin@linux.ibm.com Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman

Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

2023-06-29T20:18:36Z

Pull ext4 updates from Ted Ts'o: "Various cleanups and bug fixes in ext4's extent status tree, journalling, and block allocator subsystems. Also improve performance for parallel DIO overwrites" * tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (55 commits) ext4: avoid updating the superblock on a r/o mount if not needed jbd2: skip reading super block if it has been verified ext4: fix to check return value of freeze_bdev() in ext4_shutdown() ext4: refactoring to use the unified helper ext4_quotas_off() ext4: turn quotas off if mount failed after enabling quotas ext4: update doc about journal superblock description ext4: add journal cycled recording support jbd2: continue to record log between each mount jbd2: remove j_format_version jbd2: factor out journal initialization from journal_get_superblock() jbd2: switch to check format version in superblock directly jbd2: remove unused feature macros ext4: ext4_put_super: Remove redundant checking for 'sbi->s_journal_bdev' ext4: Fix reusing stale buffer heads from last failed mounting ext4: allow concurrent unaligned dio overwrites ext4: clean up mballoc criteria comments ext4: make ext4_zeroout_es() return void ext4: make ext4_es_insert_extent() return void ext4: make ext4_es_insert_delayed_block() return void ext4: make ext4_es_remove_extent() return void ...

Merge tag 'mm-stable-2023-06-24-19-15' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2023-06-28T17:28:11Z

Pull mm updates from Andrew Morton: - Yosry Ahmed brought back some cgroup v1 stats in OOM logs - Yosry has also eliminated cgroup's atomic rstat flushing - Nhat Pham adds the new cachestat() syscall. It provides userspace with the ability to query pagecache status - a similar concept to mincore() but more powerful and with improved usability - Mel Gorman provides more optimizations for compaction, reducing the prevalence of page rescanning - Lorenzo Stoakes has done some maintanance work on the get_user_pages() interface - Liam Howlett continues with cleanups and maintenance work to the maple tree code. Peng Zhang also does some work on maple tree - Johannes Weiner has done some cleanup work on the compaction code - David Hildenbrand has contributed additional selftests for get_user_pages() - Thomas Gleixner has contributed some maintenance and optimization work for the vmalloc code - Baolin Wang has provided some compaction cleanups, - SeongJae Park continues maintenance work on the DAMON code - Huang Ying has done some maintenance on the swap code's usage of device refcounting - Christoph Hellwig has some cleanups for the filemap/directio code - Ryan Roberts provides two patch series which yield some rationalization of the kernel's access to pte entries - use the provided APIs rather than open-coding accesses - Lorenzo Stoakes has some fixes to the interaction between pagecache and directio access to file mappings - John Hubbard has a series of fixes to the MM selftesting code - ZhangPeng continues the folio conversion campaign - Hugh Dickins has been working on the pagetable handling code, mainly with a view to reducing the load on the mmap_lock - Catalin Marinas has reduced the arm64 kmalloc() minimum alignment from 128 to 8 - Domenico Cerasuolo has improved the zswap reclaim mechanism by reorganizing the LRU management - Matthew Wilcox provides some fixups to make gfs2 work better with the buffer_head code - Vishal Moola also has done some folio conversion work - Matthew Wilcox has removed the remnants of the pagevec code - their functionality is migrated over to struct folio_batch * tag 'mm-stable-2023-06-24-19-15' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (380 commits) mm/hugetlb: remove hugetlb_set_page_subpool() mm: nommu: correct the range of mmap_sem_read_lock in task_mem() hugetlb: revert use of page_cache_next_miss() Revert "page cache: fix page_cache_next/prev_miss off by one" mm/vmscan: fix root proactive reclaim unthrottling unbalanced node mm: memcg: rename and document global_reclaim() mm: kill [add|del]_page_to_lru_list() mm: compaction: convert to use a folio in isolate_migratepages_block() mm: zswap: fix double invalidate with exclusive loads mm: remove unnecessary pagevec includes mm: remove references to pagevec mm: rename invalidate_mapping_pagevec to mapping_try_invalidate mm: remove struct pagevec net: convert sunrpc from pagevec to folio_batch i915: convert i915_gpu_error to use a folio_batch pagevec: rename fbatch_count() mm: remove check_move_unevictable_pages() drm: convert drm_gem_put_pages() to use a folio_batch i915: convert shmem_sg_free_table() to use a folio_batch scatterlist: add sg_set_folio() ...

ext4: make ext4_es_insert_extent() return void

2023-06-26T23:35:12Z

Now ext4_es_insert_extent() never return error, so make it return void. Signed-off-by: Baokun Li Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20230424033846.4732-12-libaokun1@huawei.com Signed-off-by: Theodore Ts'o

ext4: make ext4_es_insert_delayed_block() return void

2023-06-26T23:35:12Z

Now it never fails when inserting a delay extent, so the return value in ext4_es_insert_delayed_block is no longer necessary, let it return void. [ Fixed bug which caused system hangs during bigalloc test runs. See https://lore.kernel.org/r/20230612030405.GH1436857@mit.edu for more details. -- TYT ] Signed-off-by: Baokun Li Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20230424033846.4732-11-libaokun1@huawei.com Signed-off-by: Theodore Ts'o

ext4: make ext4_es_remove_extent() return void

2023-06-26T23:35:12Z

Now ext4_es_remove_extent() never fails, so make it return void. Signed-off-by: Baokun Li Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20230424033846.4732-10-libaokun1@huawei.com Signed-off-by: Theodore Ts'o

ext4: only update i_reserved_data_blocks on successful block allocation

2023-06-26T23:34:56Z

In our fault injection test, we create an ext4 file, migrate it to non-extent based file, then punch a hole and finally trigger a WARN_ON in the ext4_da_update_reserve_space(): EXT4-fs warning (device sda): ext4_da_update_reserve_space:369: ino 14, used 11 with only 10 reserved data blocks When writing back a non-extent based file, if we enable delalloc, the number of reserved blocks will be subtracted from the number of blocks mapped by ext4_ind_map_blocks(), and the extent status tree will be updated. We update the extent status tree by first removing the old extent_status and then inserting the new extent_status. If the block range we remove happens to be in an extent, then we need to allocate another extent_status with ext4_es_alloc_extent(). use old to remove to add new |----------|------------|------------| old extent_status The problem is that the allocation of a new extent_status failed due to a fault injection, and __es_shrink() did not get free memory, resulting in a return of -ENOMEM. Then do_writepages() retries after receiving -ENOMEM, we map to the same extent again, and the number of reserved blocks is again subtracted from the number of blocks in that extent. Since the blocks in the same extent are subtracted twice, we end up triggering WARN_ON at ext4_da_update_reserve_space() because used > ei->i_reserved_data_blocks. For non-extent based file, we update the number of reserved blocks after ext4_ind_map_blocks() is executed, which causes a problem that when we call ext4_ind_map_blocks() to create a block, it doesn't always create a block, but we always reduce the number of reserved blocks. So we move the logic for updating reserved blocks to ext4_ind_map_blocks() to ensure that the number of reserved blocks is updated only after we do succeed in allocating some new blocks. Fixes: 5f634d064c70 ("ext4: Fix quota accounting error with fallocate") Cc: stable@kernel.org Signed-off-by: Baokun Li Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20230424033846.4732-2-libaokun1@huawei.com Signed-off-by: Theodore Ts'o

buffer: convert page_zero_new_buffers() to folio_zero_new_buffers()

2023-06-19T23:19:31Z

Most of the callers already have a folio; convert reiserfs_write_end() to have a folio. Removes a couple of hidden calls to compound_head(). Link: https://lkml.kernel.org/r/20230612210141.730128-10-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Cc: Andreas Gruenbacher Cc: Bob Peterson Cc: Hannes Reinecke Cc: Luis Chamberlain Signed-off-by: Andrew Morton

ext4: Make ext4_write_inline_data_end() use folio

2023-06-15T04:02:10Z

ext4_write_inline_data_end() is completely converted to work with folio. Also all callers of ext4_write_inline_data_end() already works on folio except ext4_da_write_end(). Mostly for consistency and saving few instructions maybe, this patch just converts ext4_da_write_end() to work with folio which makes the last caller of ext4_write_inline_data_end() also converted to work with folio. We then make ext4_write_inline_data_end() take folio instead of page. Reviewed-by: Matthew Wilcox (Oracle) Signed-off-by: Ritesh Harjani (IBM) Link: https://lore.kernel.org/r/1bcea771720ff451a5a59b3f1bcd5fae51cb7ce7.1684122756.git.ritesh.list@gmail.com Signed-off-by: Theodore Ts'o

ext4: Make mpage_journal_page_buffers use folio

2023-06-15T04:02:10Z

This patch converts mpage_journal_page_buffers() to use folio and also removes the PAGE_SIZE assumption. Signed-off-by: Ritesh Harjani (IBM) Reviewed-by: Matthew Wilcox (Oracle) Link: https://lore.kernel.org/r/ebc3ac80e6a54b53327740d010ce684a83512021.1684122756.git.ritesh.list@gmail.com Signed-off-by: Theodore Ts'o