On NFSv3, in normal circumstances, NFS_ATTR_FATTR_MOUNTED_ON_FILEID is
not set on fattr->valid. It is only set in nfs3_decode_dirent() if
entry->fattr->fileid != entry->ino, which typically only happens for
mountpoints. (See 1ae04b252351 NFSv3: Use the readdir fileid as the
mounted-on-fileid.)
nfs_fileid_valid() returns 'ret1 || ret2', initializing both ret1 and
ret2 to true, but sets them only conditionally. Therefore, in normal
circumstances, nfs_fileid_valid() wrongly returns 'false || true' when
the fileid has changed.
There is another bug in this function for NFSv4: a server may return a
fattr with NFS_ATTR_FATTR_FILEID|NFS_ATTR_FATTR_MOUNTED_ON_FILEID.
nfs_fileid_valid() will fail to detect a change in fileid in the case
where the fattr->fileid happens to match, by chance, the stored
nfsi->fileid (copied from a previous fattr->mounted_on_fileid).
If this is a mountpoint, the current fattr->fileid and the old
fattr->mounted_on_fileid come from different filesystems and may well
happen to be identical.
The condition should be written as an if / else if:
if (fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID)
else if (fattr->valid & NFS_ATTR_FATTR_FILEID)
as is done elsewhere in NFSv4 code.
---
fs/nfs/inode.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 7d893543cf3b..e1ad5ec75795 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1717,13 +1717,11 @@ EXPORT_SYMBOL_GPL(nfs_post_op_update_inode_force_wcc);
static inline bool nfs_fileid_valid(struct nfs_inode *nfsi,
struct nfs_fattr *fattr)
{
- bool ret1 = true, ret2 = true;
-
- if (fattr->valid & NFS_ATTR_FATTR_FILEID)
- ret1 = (nfsi->fileid == fattr->fileid);
if (fattr->valid & NFS_ATTR_FATTR_MOUNTED_ON_FILEID)
- ret2 = (nfsi->fileid == fattr->mounted_on_fileid);
- return ret1 || ret2;
+ return nfsi->fileid == fattr->mounted_on_fileid;
+ else if (fattr->valid & NFS_ATTR_FATTR_FILEID)
+ return nfsi->fileid == fattr->fileid;
+ return true;
}
/*
--
2.16.2
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