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Date: Thu, 28 Apr 2022 18:57:25 +0200
From: Jan Kara <jack@...e.cz>
To: Baokun Li <libaokun1@...wei.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu,
adilger.kernel@...ger.ca, jack@...e.cz,
linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
yebin10@...wei.com, yukuai3@...wei.com, stable@...r.kernel.org,
Hulk Robot <hulkci@...wei.com>
Subject: Re: [PATCH v3] ext4: fix race condition between ext4_write and
ext4_convert_inline_data
On Thu 28-04-22 21:40:31, Baokun Li wrote:
> 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@...r.kernel.org
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Baokun Li <libaokun1@...wei.com>
Looks good to me. Feel free to add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> 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.
> --
> 2.31.1
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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