Re: [PATCH v2] ext4: skip eof zeroing when the zero range covers the eof block

[sashiko-bot@kernel.org]

> ext4_zero_range() drops the page cache of the range before allocating,
> to avoid exposing stale cached data.  However, the dropped page can be
> read back by the eof zeroing:
> 
>   fallocate(fd, FALLOC_FL_ZERO_RANGE, 0, 4096)
>     ext4_zero_range()
>       ext4_truncate_page_cache_block_range(0, 4096)
>         truncate_pagecache_range(0, 4095)
>           truncate_inode_pages_range()
>             delete_from_page_cache_batch()  # drops the page
>       ext4_alloc_file_blocks(..., 4096)
>         ext4_block_zero_eof(512, LLONG_MAX) # not block aligned
>           ext4_load_tail_bh()
>              __filemap_get_folio(FGP_WRITEBEGIN | FGP_ACCESSED)
>              # FGP_CREAT reads the dropped page back
> [ ... ]
> 
> Fixes: c4602a1d09ec ("ext4: move zero partial block range functions out of active handle")
> Fixes: f4265b8d32c4 ("ext4: add FALLOC_FL_WRITE_ZEROES support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Baokun Li <libaokun@linux.alibaba.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261022122625.1744363-1-libaokun@linux.alibaba.com?part=1