From: Darrick J. Wong darrick.wong@oracle.com
[ Upstream commit 07d19dc9fbe9128378b9e226abe886fd8fd473df ]
A deduplication data corruption is exposed in XFS and btrfs. It is caused by extending the block match range to include the partial EOF block, but then allowing unknown data beyond EOF to be considered a "match" to data in the destination file because the comparison is only made to the end of the source file. This corrupts the destination file when the source extent is shared with it.
The VFS remapping prep functions only support whole block dedupe, but we still need to appear to support whole file dedupe correctly. Hence if the dedupe request includes the last block of the souce file, don't include it in the actual dedupe operation. If the rest of the range dedupes successfully, then reject the entire request. A subsequent patch will enable us to shorten dedupe requests correctly.
When reflinking sub-file ranges, a data corruption can occur when the source file range includes a partial EOF block. This shares the unknown data beyond EOF into the second file at a position inside EOF, exposing stale data in the second file.
If the reflink request includes the last block of the souce file, only proceed with the reflink operation if it lands at or past the destination file's current EOF. If it lands within the destination file EOF, reject the entire request with -EINVAL and make the caller go the hard way. A subsequent patch will enable us to shorten reflink requests correctly.
Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Dave Chinner david@fromorbit.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/read_write.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+)
diff --git a/fs/read_write.c b/fs/read_write.c index 5fb5ee5b8cd70..2195380620d02 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -1715,6 +1715,34 @@ static int clone_verify_area(struct file *file, loff_t pos, u64 len, bool write)
return security_file_permission(file, write ? MAY_WRITE : MAY_READ); } +/* + * Ensure that we don't remap a partial EOF block in the middle of something + * else. Assume that the offsets have already been checked for block + * alignment. + * + * For deduplication we always scale down to the previous block because we + * can't meaningfully compare post-EOF contents. + * + * For clone we only link a partial EOF block above the destination file's EOF. + */ +static int generic_remap_check_len(struct inode *inode_in, + struct inode *inode_out, + loff_t pos_out, + u64 *len, + bool is_dedupe) +{ + u64 blkmask = i_blocksize(inode_in) - 1; + + if ((*len & blkmask) == 0) + return 0; + + if (is_dedupe) + *len &= ~blkmask; + else if (pos_out + *len < i_size_read(inode_out)) + return -EINVAL; + + return 0; +}
/* * Check that the two inodes are eligible for cloning, the ranges make @@ -1821,6 +1849,11 @@ int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in, return -EBADE; }
+ ret = generic_remap_check_len(inode_in, inode_out, pos_out, len, + is_dedupe); + if (ret) + return ret; + return 1; } EXPORT_SYMBOL(vfs_clone_file_prep_inodes);