kernel/fs/overlayfs/export.c, branch linux-5.1.y

ovl: fix decode of dir file handle with multi lower layers

2018-11-21T09:44:48Z

When decoding a lower file handle, we first call ovl_check_origin_fh() with connected=false to get any real lower dentry for overlay inode cache lookup. If the real dentry is a disconnected dir dentry, ovl_check_origin_fh() is called again with connected=true to get a connected real dentry and find the lower layer the real dentry belongs to. If the first call returned a connected real dentry, we use it to lookup an overlay connected dentry, but the first ovl_check_origin_fh() call with connected=false did not check that the found dentry is under the root of the layer (see ovl_acceptable()), it only checked that the found dentry super block matches the uuid of the lower file handle. In case there are multiple lower layers on the same fs and the found dentry is not from the top most lower layer, using the layer index returned from the first ovl_check_origin_fh() is wrong and we end up failing to decode the file handle. Fix this by always calling ovl_check_origin_fh() with connected=true if we got a directory dentry in the first call. Fixes: 8b58924ad55c ("ovl: lookup in inode cache first when decoding...") Cc: # v4.17 Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: Modify ovl_lookup() and friends to lookup metacopy dentry

2018-07-20T07:56:09Z

This patch modifies ovl_lookup() and friends to lookup metacopy dentries. It also allows for presence of metacopy dentries in lower layer. During lookup, check for presence of OVL_XATTR_METACOPY and if not present, set OVL_UPPERDATA bit in flags. We don't support metacopy feature with nfs_export. So in nfs_export code, we set OVL_UPPERDATA flag set unconditionally if upper inode exists. Do not follow metacopy origin if we find a metacopy only inode and metacopy feature is not enabled for that mount. Like redirect, this can have security implications where an attacker could hand craft upper and try to gain access to file on lower which it should not have to begin with. Signed-off-by: Vivek Goyal Reviewed-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: Pass argument to ovl_get_inode() in a structure

2018-05-31T09:06:12Z

ovl_get_inode() right now has 5 parameters. Soon this patch series will add 2 more and suddenly argument list starts looking too long. Hence pass arguments to ovl_get_inode() in a structure and it looks little cleaner. Signed-off-by: Vivek Goyal Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: consistent i_ino for non-samefs with xino

2018-04-12T10:04:50Z

When overlay layers are not all on the same fs, but all inode numbers of underlying fs do not use the high 'xino' bits, overlay st_ino values are constant and persistent. In that case, set i_ino value to the same value as st_ino for nfsd readdirplus validator. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: cleanup setting OVL_INDEX

2018-04-12T10:04:49Z

Signed-off-by: Miklos Szeredi

ovl: lookup in inode cache first when decoding lower file handle

2018-04-12T10:04:49Z

When decoding a lower file handle, we need to check if lower file was copied up and indexed and if it has a whiteout index, we need to check if this is an unlinked but open non-dir before returning -ESTALE. To find out if this is an unlinked but open non-dir we need to lookup an overlay inode in inode cache by lower inode and that requires decoding the lower file handle before looking in inode cache. Before this change, if the lower inode turned out to be a directory, we may have paid an expensive cost to reconnect that lower directory for nothing. After this change, we start by decoding a disconnected lower dentry and using the lower inode for looking up an overlay inode in inode cache. If we find overlay inode and dentry in cache, we avoid the index lookup overhead. If we don't find an overlay inode and dentry in cache, then we only need to decode a connected lower dentry in case the lower dentry is a non-indexed directory. The xfstests group overlay/exportfs tests decoding overlayfs file handles after drop_caches with different states of the file at encode and decode time. Overall the tests in the group call ovl_lower_fh_to_d() 89 times to decode a lower file handle. Before this change, the tests called ovl_get_index_fh() 75 times and reconnect_one() 61 times. After this change, the tests call ovl_get_index_fh() 70 times and reconnect_one() 59 times. The 2 cases where reconnect_one() was avoided are cases where a non-upper directory file handle was encoded, then the directory removed and then file handle was decoded. To demonstrate the affect on decoding file handles with hot inode/dentry cache, the drop_caches call in the tests was disabled. Without drop_caches, there are no reconnect_one() calls at all before or after the change. Before the change, there are 75 calls to ovl_get_index_fh(), exactly as the case with drop_caches. After the change, there are only 10 calls to ovl_get_index_fh(). Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: do not try to reconnect a disconnected origin dentry

2018-04-12T10:04:49Z

On lookup of non directory, we try to decode the origin file handle stored in upper inode. The origin file handle is supposed to be decoded to a disconnected non-dir dentry, which is fine, because we only need the lower inode of a copy up origin. However, if the origin file handle somehow turns out to be a directory we pay the expensive cost of reconnecting the directory dentry, only to get a mismatch file type and drop the dentry. Optimize this case by explicitly opting out of reconnecting the dentry. Opting-out of reconnect is done by passing a NULL acceptable callback to exportfs_decode_fh(). While the case described above is a strange corner case that does not really need to be optimized, the API added for this optimization will be used by a following patch to optimize a more common case of decoding an overlayfs file handle. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: disambiguate ovl_encode_fh()

2018-04-12T10:04:49Z

Rename ovl_encode_fh() to ovl_encode_real_fh() to differentiate from the exportfs function ovl_encode_inode_fh() and change the latter to ovl_encode_fh() to match the exportfs method name. Rename ovl_decode_fh() to ovl_decode_real_fh() for consistency. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi

ovl: fix ptr_ret.cocci warnings

2018-02-26T11:45:20Z

fs/overlayfs/export.c:459:10-16: WARNING: PTR_ERR_OR_ZERO can be used Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR Generated by: scripts/coccinelle/api/ptr_ret.cocci Fixes: 4b91c30a5a19 ("ovl: lookup connected ancestor of dir in inode cache") CC: Amir Goldstein Signed-off-by: Fengguang Wu Signed-off-by: Miklos Szeredi

ovl: check ERR_PTR() return value from ovl_lookup_real()

2018-02-16T14:53:20Z

Reported-by: Dan Carpenter Fixes: 061701540349 ("ovl: lookup indexed ancestor of lower dir") Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi