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    Subject[PATCH 5.15 542/667] ext4: fix race condition between ext4_write and ext4_convert_inline_data
    Date
    From: Baokun Li <libaokun1@huawei.com>

    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@vger.kernel.org
    Reported-by: Hulk Robot <hulkci@huawei.com>
    Signed-off-by: Baokun Li <libaokun1@huawei.com>
    Reviewed-by: Jan Kara <jack@suse.cz>
    Link: https://lore.kernel.org/r/20220428134031.4153381-1-libaokun1@huawei.com
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/ext4/extents.c | 10 ++++++----
    fs/ext4/inode.c | 9 ---------
    2 files changed, 6 insertions(+), 13 deletions(-)

    --- a/fs/ext4/extents.c
    +++ b/fs/ext4/extents.c
    @@ -4699,15 +4699,17 @@ long ext4_fallocate(struct file *file, i

    ext4_fc_start_update(inode);

    + 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;
    --- a/fs/ext4/inode.c
    +++ b/fs/ext4/inode.c
    @@ -3953,15 +3953,6 @@ int ext4_punch_hole(struct file *file, l

    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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