| Message ID | 20181005012336.1418-3-david@fromorbit.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | xfs: fix another couple of reflink data corruptions | expand |
On Fri, Oct 05, 2018 at 11:23:36AM +1000, Dave Chinner wrote: > 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. > > XFS only supports whole block sharing, but we still need to > support whole file reflink correctly. Hence 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. > > This avoids the data corruption vector, but also avoids disruption > of returning EINVAL to userspace for the common case of whole file > cloning. > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > --- > fs/xfs/xfs_reflink.c | 39 +++++++++++++++++++++++++++++++-------- > 1 file changed, 31 insertions(+), 8 deletions(-) > > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c > index 6b0da1b80103..2615271603ce 100644 > --- a/fs/xfs/xfs_reflink.c > +++ b/fs/xfs/xfs_reflink.c > @@ -1229,12 +1229,24 @@ xfs_iolock_two_inodes_and_break_layout( > * hence can introduce a corruption into the file that has it's > * block replaced. > * > - * Despite this issue, we still need to report that range as successfully > - * deduped to avoid confusing userspace with EINVAL errors on completely > - * matching file data. The only time that an unaligned length will be passed to > - * us is when it spans the EOF block of the source file, so if we simply mask it > - * down to be block aligned here the we will dedupe everything but that partial > - * EOF block. > + * In similar fashion, the VFS file cloning also allows partial EOF blocks to be > + * "block aligned" for the purposes of cloning entire files. > + * However, if the source file range > + * includes the EOF block and it lands within the existing EOF of the > + * destination file, then we can expose stale data from beyond the source file > + * EOF in the destination file. > + * > + * XFs doesn't support partial block sharing, so in both cases we have check > + * these cases ourselves. For dedupe, we can simply round the length to dedupe > + * down to the previous whole block and ignore the partial EOF block. While this > + * means we can't dedupe the last block of a file, this is an acceptible > + * tradeoff for simplicity on implementation. > + * > + * For cloning, we want to share the partial EOF block if it is also the new EOF > + * block of the destination file. If the partial EOF blck lies inside the > + * existing destination EOF, then we have to abort the clone to avoid exposing > + * stale data int eh destination file. Hence we reject these clone attempts with > + * -EINVAL in this case. > */ > int > xfs_reflink_remap_range( > @@ -1255,6 +1267,7 @@ xfs_reflink_remap_range( > xfs_filblks_t fsblen; > xfs_extlen_t cowextsize; > ssize_t ret; > + u64 blkmask = i_blocksize(inode_in) - 1; > > if (!xfs_sb_version_hasreflink(&mp->m_sb)) > return -EOPNOTSUPP; > @@ -1292,8 +1305,18 @@ xfs_reflink_remap_range( > * from the source file so we don't try to dedupe the partial > * EOF block. > */ > - if (is_dedupe) > - len &= ~((u64)i_blocksize(inode_in) - 1); > + if (is_dedupe) { > + len &= ~blkmask; > + } else if (len & blkmask) { > + /* > + * The user is attempting to share a partial EOF block, > + * if it's inside the destination EOF then reject it > + */ > + if (pos_out + len < i_size_read(inode_out)) { > + ret = -EINVAL; > + goto out_unlock; Hmm... to integrate this with the new series I just posted, I think we'd decrease len to be block aligned (perhaps in generic_clone_checks) so that copy_file_range would be able to pagecache copy the last bit instead of failing the whole operation. IOWs, if (is_dedupe) { len &= ~blkmask; } else if (len & blkmask) { if (pos_out + len < size_out) { len &= ~blkmask; } } But at a first glance these two patches look ok to me. --D > + } > + } > > /* Attach dquots to dest inode before changing block map */ > ret = xfs_qm_dqattach(dest); > -- > 2.17.0 >
On Thu, Oct 04, 2018 at 06:40:14PM -0700, Darrick J. Wong wrote: > On Fri, Oct 05, 2018 at 11:23:36AM +1000, Dave Chinner wrote: > > 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. > > > > XFS only supports whole block sharing, but we still need to > > support whole file reflink correctly. Hence 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. > > > > This avoids the data corruption vector, but also avoids disruption > > of returning EINVAL to userspace for the common case of whole file > > cloning. > > > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > > --- > > fs/xfs/xfs_reflink.c | 39 +++++++++++++++++++++++++++++++-------- > > 1 file changed, 31 insertions(+), 8 deletions(-) > > > > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c > > index 6b0da1b80103..2615271603ce 100644 > > --- a/fs/xfs/xfs_reflink.c > > +++ b/fs/xfs/xfs_reflink.c > > @@ -1229,12 +1229,24 @@ xfs_iolock_two_inodes_and_break_layout( > > * hence can introduce a corruption into the file that has it's > > * block replaced. > > * > > - * Despite this issue, we still need to report that range as successfully > > - * deduped to avoid confusing userspace with EINVAL errors on completely > > - * matching file data. The only time that an unaligned length will be passed to > > - * us is when it spans the EOF block of the source file, so if we simply mask it > > - * down to be block aligned here the we will dedupe everything but that partial > > - * EOF block. > > + * In similar fashion, the VFS file cloning also allows partial EOF blocks to be > > + * "block aligned" for the purposes of cloning entire files. > > + * However, if the source file range > > + * includes the EOF block and it lands within the existing EOF of the > > + * destination file, then we can expose stale data from beyond the source file > > + * EOF in the destination file. > > + * > > + * XFs doesn't support partial block sharing, so in both cases we have check > > + * these cases ourselves. For dedupe, we can simply round the length to dedupe > > + * down to the previous whole block and ignore the partial EOF block. While this > > + * means we can't dedupe the last block of a file, this is an acceptible > > + * tradeoff for simplicity on implementation. > > + * > > + * For cloning, we want to share the partial EOF block if it is also the new EOF > > + * block of the destination file. If the partial EOF blck lies inside the > > + * existing destination EOF, then we have to abort the clone to avoid exposing > > + * stale data int eh destination file. Hence we reject these clone attempts with > > + * -EINVAL in this case. > > */ > > int > > xfs_reflink_remap_range( > > @@ -1255,6 +1267,7 @@ xfs_reflink_remap_range( > > xfs_filblks_t fsblen; > > xfs_extlen_t cowextsize; > > ssize_t ret; > > + u64 blkmask = i_blocksize(inode_in) - 1; > > > > if (!xfs_sb_version_hasreflink(&mp->m_sb)) > > return -EOPNOTSUPP; > > @@ -1292,8 +1305,18 @@ xfs_reflink_remap_range( > > * from the source file so we don't try to dedupe the partial > > * EOF block. > > */ > > - if (is_dedupe) > > - len &= ~((u64)i_blocksize(inode_in) - 1); > > + if (is_dedupe) { > > + len &= ~blkmask; > > + } else if (len & blkmask) { > > + /* > > + * The user is attempting to share a partial EOF block, > > + * if it's inside the destination EOF then reject it > > + */ > > + if (pos_out + len < i_size_read(inode_out)) { > > + ret = -EINVAL; > > + goto out_unlock; > > Hmm... to integrate this with the new series I just posted, I think we'd > decrease len to be block aligned (perhaps in generic_clone_checks) so > that copy_file_range would be able to pagecache copy the last bit > instead of failing the whole operation. IOWs, > > if (is_dedupe) { > len &= ~blkmask; > } else if (len & blkmask) { > if (pos_out + len < size_out) { > len &= ~blkmask; > } > } OK. But if I'm going to push it with just the EOF zeroing and ctime/suid fixes, then this doesn't change until the handling of partial completion is added to XFS later in the patchset, right? Cheers, Dave.
On Fri, Oct 05, 2018 at 03:21:21PM +1000, Dave Chinner wrote: > On Thu, Oct 04, 2018 at 06:40:14PM -0700, Darrick J. Wong wrote: > > On Fri, Oct 05, 2018 at 11:23:36AM +1000, Dave Chinner wrote: > > > 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. > > > > > > XFS only supports whole block sharing, but we still need to > > > support whole file reflink correctly. Hence 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. > > > > > > This avoids the data corruption vector, but also avoids disruption > > > of returning EINVAL to userspace for the common case of whole file > > > cloning. > > > > > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > > > --- > > > fs/xfs/xfs_reflink.c | 39 +++++++++++++++++++++++++++++++-------- > > > 1 file changed, 31 insertions(+), 8 deletions(-) > > > > > > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c > > > index 6b0da1b80103..2615271603ce 100644 > > > --- a/fs/xfs/xfs_reflink.c > > > +++ b/fs/xfs/xfs_reflink.c > > > @@ -1229,12 +1229,24 @@ xfs_iolock_two_inodes_and_break_layout( > > > * hence can introduce a corruption into the file that has it's > > > * block replaced. > > > * > > > - * Despite this issue, we still need to report that range as successfully > > > - * deduped to avoid confusing userspace with EINVAL errors on completely > > > - * matching file data. The only time that an unaligned length will be passed to > > > - * us is when it spans the EOF block of the source file, so if we simply mask it > > > - * down to be block aligned here the we will dedupe everything but that partial > > > - * EOF block. > > > + * In similar fashion, the VFS file cloning also allows partial EOF blocks to be > > > + * "block aligned" for the purposes of cloning entire files. > > > + * However, if the source file range > > > + * includes the EOF block and it lands within the existing EOF of the > > > + * destination file, then we can expose stale data from beyond the source file > > > + * EOF in the destination file. > > > + * > > > + * XFs doesn't support partial block sharing, so in both cases we have check > > > + * these cases ourselves. For dedupe, we can simply round the length to dedupe > > > + * down to the previous whole block and ignore the partial EOF block. While this > > > + * means we can't dedupe the last block of a file, this is an acceptible > > > + * tradeoff for simplicity on implementation. > > > + * > > > + * For cloning, we want to share the partial EOF block if it is also the new EOF > > > + * block of the destination file. If the partial EOF blck lies inside the > > > + * existing destination EOF, then we have to abort the clone to avoid exposing > > > + * stale data int eh destination file. Hence we reject these clone attempts with > > > + * -EINVAL in this case. > > > */ > > > int > > > xfs_reflink_remap_range( > > > @@ -1255,6 +1267,7 @@ xfs_reflink_remap_range( > > > xfs_filblks_t fsblen; > > > xfs_extlen_t cowextsize; > > > ssize_t ret; > > > + u64 blkmask = i_blocksize(inode_in) - 1; > > > > > > if (!xfs_sb_version_hasreflink(&mp->m_sb)) > > > return -EOPNOTSUPP; > > > @@ -1292,8 +1305,18 @@ xfs_reflink_remap_range( > > > * from the source file so we don't try to dedupe the partial > > > * EOF block. > > > */ > > > - if (is_dedupe) > > > - len &= ~((u64)i_blocksize(inode_in) - 1); > > > + if (is_dedupe) { > > > + len &= ~blkmask; > > > + } else if (len & blkmask) { > > > + /* > > > + * The user is attempting to share a partial EOF block, > > > + * if it's inside the destination EOF then reject it > > > + */ > > > + if (pos_out + len < i_size_read(inode_out)) { > > > + ret = -EINVAL; > > > + goto out_unlock; > > > > Hmm... to integrate this with the new series I just posted, I think we'd > > decrease len to be block aligned (perhaps in generic_clone_checks) so > > that copy_file_range would be able to pagecache copy the last bit > > instead of failing the whole operation. IOWs, > > > > if (is_dedupe) { > > len &= ~blkmask; > > } else if (len & blkmask) { > > if (pos_out + len < size_out) { > > len &= ~blkmask; > > } > > } > > OK. But if I'm going to push it with just the EOF zeroing and > ctime/suid fixes, then this doesn't change until the handling of > partial completion is added to XFS later in the patchset, right? Right. If you add this series before the partial completion patches I'll fix things up when I rebase that part of my series. --D > Cheers, > > Dave. > > -- > Dave Chinner > david@fromorbit.com
On Fri, Oct 05, 2018 at 11:23:36AM +1000, Dave Chinner wrote: > 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. > > XFS only supports whole block sharing, but we still need to > support whole file reflink correctly. Hence 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. > > This avoids the data corruption vector, but also avoids disruption > of returning EINVAL to userspace for the common case of whole file > cloning. > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > --- > fs/xfs/xfs_reflink.c | 39 +++++++++++++++++++++++++++++++-------- > 1 file changed, 31 insertions(+), 8 deletions(-) > > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c > index 6b0da1b80103..2615271603ce 100644 > --- a/fs/xfs/xfs_reflink.c > +++ b/fs/xfs/xfs_reflink.c > @@ -1229,12 +1229,24 @@ xfs_iolock_two_inodes_and_break_layout( > * hence can introduce a corruption into the file that has it's > * block replaced. > * > - * Despite this issue, we still need to report that range as successfully > - * deduped to avoid confusing userspace with EINVAL errors on completely > - * matching file data. The only time that an unaligned length will be passed to > - * us is when it spans the EOF block of the source file, so if we simply mask it > - * down to be block aligned here the we will dedupe everything but that partial > - * EOF block. > + * In similar fashion, the VFS file cloning also allows partial EOF blocks to be > + * "block aligned" for the purposes of cloning entire files. > + * However, if the source file range > + * includes the EOF block and it lands within the existing EOF of the > + * destination file, then we can expose stale data from beyond the source file > + * EOF in the destination file. > + * > + * XFs doesn't support partial block sharing, so in both cases we have check > + * these cases ourselves. For dedupe, we can simply round the length to dedupe > + * down to the previous whole block and ignore the partial EOF block. While this > + * means we can't dedupe the last block of a file, this is an acceptible > + * tradeoff for simplicity on implementation. > + * > + * For cloning, we want to share the partial EOF block if it is also the new EOF > + * block of the destination file. If the partial EOF blck lies inside the > + * existing destination EOF, then we have to abort the clone to avoid exposing > + * stale data int eh destination file. Hence we reject these clone attempts with > + * -EINVAL in this case. > */ > int > xfs_reflink_remap_range( > @@ -1255,6 +1267,7 @@ xfs_reflink_remap_range( > xfs_filblks_t fsblen; > xfs_extlen_t cowextsize; > ssize_t ret; > + u64 blkmask = i_blocksize(inode_in) - 1; > > if (!xfs_sb_version_hasreflink(&mp->m_sb)) > return -EOPNOTSUPP; > @@ -1292,8 +1305,18 @@ xfs_reflink_remap_range( > * from the source file so we don't try to dedupe the partial > * EOF block. > */ > - if (is_dedupe) > - len &= ~((u64)i_blocksize(inode_in) - 1); > + if (is_dedupe) { > + len &= ~blkmask; > + } else if (len & blkmask) { > + /* > + * The user is attempting to share a partial EOF block, > + * if it's inside the destination EOF then reject it > + */ > + if (pos_out + len < i_size_read(inode_out)) { > + ret = -EINVAL; > + goto out_unlock; Same comment about reporting truncated lengths back to userspace as the last patch, but nevertheless: Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> --D > + } > + } > > /* Attach dquots to dest inode before changing block map */ > ret = xfs_qm_dqattach(dest); > -- > 2.17.0 >
Looks fine:
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c index 6b0da1b80103..2615271603ce 100644 --- a/fs/xfs/xfs_reflink.c +++ b/fs/xfs/xfs_reflink.c @@ -1229,12 +1229,24 @@ xfs_iolock_two_inodes_and_break_layout( * hence can introduce a corruption into the file that has it's * block replaced. * - * Despite this issue, we still need to report that range as successfully - * deduped to avoid confusing userspace with EINVAL errors on completely - * matching file data. The only time that an unaligned length will be passed to - * us is when it spans the EOF block of the source file, so if we simply mask it - * down to be block aligned here the we will dedupe everything but that partial - * EOF block. + * In similar fashion, the VFS file cloning also allows partial EOF blocks to be + * "block aligned" for the purposes of cloning entire files. + * However, if the source file range + * includes the EOF block and it lands within the existing EOF of the + * destination file, then we can expose stale data from beyond the source file + * EOF in the destination file. + * + * XFs doesn't support partial block sharing, so in both cases we have check + * these cases ourselves. For dedupe, we can simply round the length to dedupe + * down to the previous whole block and ignore the partial EOF block. While this + * means we can't dedupe the last block of a file, this is an acceptible + * tradeoff for simplicity on implementation. + * + * For cloning, we want to share the partial EOF block if it is also the new EOF + * block of the destination file. If the partial EOF blck lies inside the + * existing destination EOF, then we have to abort the clone to avoid exposing + * stale data int eh destination file. Hence we reject these clone attempts with + * -EINVAL in this case. */ int xfs_reflink_remap_range( @@ -1255,6 +1267,7 @@ xfs_reflink_remap_range( xfs_filblks_t fsblen; xfs_extlen_t cowextsize; ssize_t ret; + u64 blkmask = i_blocksize(inode_in) - 1; if (!xfs_sb_version_hasreflink(&mp->m_sb)) return -EOPNOTSUPP; @@ -1292,8 +1305,18 @@ xfs_reflink_remap_range( * from the source file so we don't try to dedupe the partial * EOF block. */ - if (is_dedupe) - len &= ~((u64)i_blocksize(inode_in) - 1); + if (is_dedupe) { + len &= ~blkmask; + } else if (len & blkmask) { + /* + * The user is attempting to share a partial EOF block, + * if it's inside the destination EOF then reject it + */ + if (pos_out + len < i_size_read(inode_out)) { + ret = -EINVAL; + goto out_unlock; + } + } /* Attach dquots to dest inode before changing block map */ ret = xfs_qm_dqattach(dest);
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. XFS only supports whole block sharing, but we still need to support whole file reflink correctly. Hence 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. This avoids the data corruption vector, but also avoids disruption of returning EINVAL to userspace for the common case of whole file cloning. Signed-off-by: Dave Chinner <dchinner@redhat.com> --- fs/xfs/xfs_reflink.c | 39 +++++++++++++++++++++++++++++++-------- 1 file changed, 31 insertions(+), 8 deletions(-)