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erofs: ensure m_llen is reset to 0 if metadata is invalid

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[ Upstream commit 9b32b063be1001e322c5f6e01f2a649636947851 ]

Sometimes, the on-disk metadata might be invalid due to user
interrupts, storage failures, or other unknown causes.

In that case, z_erofs_map_blocks_iter() may still return a valid
m_llen while other fields remain invalid (e.g., m_plen can be 0).

Due to the return value of z_erofs_scan_folio() in some path will
be ignored on purpose, the following z_erofs_scan_folio() could
then use the invalid value by accident.

Let's reset m_llen to 0 to prevent this.

Link: https://lore.kernel.org/r/20240629185743.2819229-1-hsiangkao@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Gao Xiang 2024-06-30 02:57:43 +08:00 committed by Greg Kroah-Hartman
parent 605572e64c
commit e424638474
1 changed files with 2 additions and 0 deletions
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2
fs/erofs/zmap.c
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@ -763,6 +763,8 @@ int z_erofs_map_blocks_iter(struct inode *inode, struct erofs_map_blocks *map,
err = z_erofs_do_map_blocks(inode, map, flags);
out:
if (err)
map->m_llen = 0;
trace_z_erofs_map_blocks_iter_exit(inode, map, flags, err);
/* aggressively BUG_ON iff CONFIG_EROFS_FS_DEBUG is on */