Re: [PATCH v3] ext4: fix race condition between ext4_write and ext4_convert_inline_data

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A gentle ping.

在 2022/4/28 21:40, Baokun Li 写道:
Hulk Robot reported a BUG_ON:
  ==================================================================
  EXT4-fs error (device loop3): ext4_mb_generate_buddy:805: group 0,
  block bitmap and bg descriptor inconsistent: 25 vs 31513 free clusters
  kernel BUG at fs/ext4/ext4_jbd2.c:53!
  invalid opcode: 0000 [#1] SMP KASAN PTI
  CPU: 0 PID: 25371 Comm: syz-executor.3 Not tainted 5.10.0+ #1
  RIP: 0010:ext4_put_nojournal fs/ext4/ext4_jbd2.c:53 [inline]
  RIP: 0010:__ext4_journal_stop+0x10e/0x110 fs/ext4/ext4_jbd2.c:116
  [...]
  Call Trace:
   ext4_write_inline_data_end+0x59a/0x730 fs/ext4/inline.c:795
   generic_perform_write+0x279/0x3c0 mm/filemap.c:3344
   ext4_buffered_write_iter+0x2e3/0x3d0 fs/ext4/file.c:270
   ext4_file_write_iter+0x30a/0x11c0 fs/ext4/file.c:520
   do_iter_readv_writev+0x339/0x3c0 fs/read_write.c:732
   do_iter_write+0x107/0x430 fs/read_write.c:861
   vfs_writev fs/read_write.c:934 [inline]
   do_pwritev+0x1e5/0x380 fs/read_write.c:1031
  [...]
  ==================================================================

Above issue may happen as follows:
            cpu1                     cpu2
__________________________|__________________________
do_pwritev
  vfs_writev
   do_iter_write
    ext4_file_write_iter
     ext4_buffered_write_iter
      generic_perform_write
       ext4_da_write_begin
                            vfs_fallocate
                             ext4_fallocate
                              ext4_convert_inline_data
                               ext4_convert_inline_data_nolock
                                ext4_destroy_inline_data_nolock
                                 clear EXT4_STATE_MAY_INLINE_DATA
                                ext4_map_blocks
                                 ext4_ext_map_blocks
                                  ext4_mb_new_blocks
                                   ext4_mb_regular_allocator
                                    ext4_mb_good_group_nolock
                                     ext4_mb_init_group
                                      ext4_mb_init_cache
                                       ext4_mb_generate_buddy  --> error
        ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)
                                 ext4_restore_inline_data
                                  set EXT4_STATE_MAY_INLINE_DATA
        ext4_block_write_begin
       ext4_da_write_end
        ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)
        ext4_write_inline_data_end
         handle=NULL
         ext4_journal_stop(handle)
          __ext4_journal_stop
           ext4_put_nojournal(handle)
            ref_cnt = (unsigned long)handle
            BUG_ON(ref_cnt == 0)  ---> BUG_ON

The lock held by ext4_convert_inline_data is xattr_sem, but the lock
held by generic_perform_write is i_rwsem. Therefore, the two locks can
be concurrent.

To solve above issue, we add inode_lock() for ext4_convert_inline_data().
At the same time, move ext4_convert_inline_data() in front of
ext4_punch_hole(), remove similar handling from ext4_punch_hole().

Fixes: 0c8d414f163f ("ext4: let fallocate handle inline data correctly")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
---
V1->V2:
	Increase the range of the inode_lock.
V2->V3:
	Move the lock outside the ext4_convert_inline_data().
	And reorganize ext4_fallocate().

  fs/ext4/extents.c | 10 ++++++----
  fs/ext4/inode.c   |  9 ---------
  2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index e473fde6b64b..474479ce76e0 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4693,15 +4693,17 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
  		     FALLOC_FL_INSERT_RANGE))
  		return -EOPNOTSUPP;
+ inode_lock(inode);
+	ret = ext4_convert_inline_data(inode);
+	inode_unlock(inode);
+	if (ret)
+		goto exit;
+
  	if (mode & FALLOC_FL_PUNCH_HOLE) {
  		ret = ext4_punch_hole(file, offset, len);
  		goto exit;
  	}
- ret = ext4_convert_inline_data(inode);
-	if (ret)
-		goto exit;
-
  	if (mode & FALLOC_FL_COLLAPSE_RANGE) {
  		ret = ext4_collapse_range(file, offset, len);
  		goto exit;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 646ece9b3455..4779673d733e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3967,15 +3967,6 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
trace_ext4_punch_hole(inode, offset, length, 0); - ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
-	if (ext4_has_inline_data(inode)) {
-		filemap_invalidate_lock(mapping);
-		ret = ext4_convert_inline_data(inode);
-		filemap_invalidate_unlock(mapping);
-		if (ret)
-			return ret;
-	}
-
  	/*
  	 * Write out all dirty pages to avoid race conditions
  	 * Then release them.





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