[PATCH 5.4 18/71] ext4: fix race condition between ext4_write and ext4_convert_inline_data

[Greg Kroah-Hartman]

From: Baokun Li <libaokun1@xxxxxxxxxx>

commit f87c7a4b084afc13190cbb263538e444cb2b392a upstream.

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>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Link: https://lore.kernel.org/r/20220428134031.4153381-1-libaokun1@xxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/ext4/extents.c |    8 +++++---
 fs/ext4/inode.c   |    9 ---------
 2 files changed, 5 insertions(+), 12 deletions(-)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4932,13 +4932,15 @@ long ext4_fallocate(struct file *file, i
 		     FALLOC_FL_INSERT_RANGE))
 		return -EOPNOTSUPP;
 
-	if (mode & FALLOC_FL_PUNCH_HOLE)
-		return ext4_punch_hole(inode, offset, len);
-
+	inode_lock(inode);
 	ret = ext4_convert_inline_data(inode);
+	inode_unlock(inode);
 	if (ret)
 		return ret;
 
+	if (mode & FALLOC_FL_PUNCH_HOLE)
+		return ext4_punch_hole(inode, offset, len);
+
 	if (mode & FALLOC_FL_COLLAPSE_RANGE)
 		return ext4_collapse_range(inode, offset, len);
 
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4322,15 +4322,6 @@ int ext4_punch_hole(struct inode *inode,
 
 	trace_ext4_punch_hole(inode, offset, length, 0);
 
-	ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
-	if (ext4_has_inline_data(inode)) {
-		down_write(&EXT4_I(inode)->i_mmap_sem);
-		ret = ext4_convert_inline_data(inode);
-		up_write(&EXT4_I(inode)->i_mmap_sem);
-		if (ret)
-			return ret;
-	}
-
 	/*
 	 * Write out all dirty pages to avoid race conditions
 	 * Then release them.