Since commit bafc9b754f75 ("vfs: More precise tests in d_invalidate")
in v3.18, a return of '0' from ->d_revalidate() will cause the dentry
to be invalidated even if it has filesystems mounted on or it or on a
descendant. The mounted filesystem is unmounted.
This means we need to be careful not to return 0 unless the directory
referred to truly is invalid. So -ESTALE or -ENOENT should invalidate
the directory. Other errors such a -EPERM or -ERESTARTSYS should be
returned from ->d_revalidate() so they are propagated to the caller.
A particular problem can be demonstrated by:
1/ mount an NFS filesystem using NFSv3 on /mnt
2/ mount any other filesystem on /mnt/foo
3/ ls /mnt/foo
4/ turn off network, or otherwise make the server unable to respond
5/ ls /mnt/foo &
6/ cat /proc/$!/stack # note that nfs_lookup_revalidate is in the call stack
7/ kill -9 $! # this results in -ERESTARTSYS being returned
8/ observe that /mnt/foo has been unmounted.
This patch changes nfs_lookup_revalidate() to only treat
-ESTALE from nfs_lookup_verify_inode() and
-ESTALE or -ENOENT from ->lookup()
as indicating an invalid inode. Other errors are returned.
Also nfs_check_inode_attributes() is changed to return -ESTALE rather
than -EIO. This is consistent with the error returned in similar
circumstances from nfs_update_inode().
As this bug allows any user to unmount a filesystem mounted on an NFS
filesystem, this fix is suitable for stable kernels.
Fixes: bafc9b754f75 ("vfs: More precise tests in d_invalidate")
Cc: stable@xxxxxxxxxxxxxxx (v3.18+)
Signed-off-by: NeilBrown <neilb@xxxxxxxx>
---
fs/nfs/dir.c | 12 ++++++++----
fs/nfs/inode.c | 4 ++--
2 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 4f0706bd387f..727c5a53417a 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1115,11 +1115,13 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
/* Force a full look up iff the parent directory has changed */
if (!nfs_is_exclusive_create(dir, flags) &&
nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU)) {
-
- if (nfs_lookup_verify_inode(inode, flags)) {
+ error = nfs_lookup_verify_inode(inode, flags);
+ if (error) {
if (flags & LOOKUP_RCU)
return -ECHILD;
- goto out_zap_parent;
+ if (error == -ESTALE)
+ goto out_zap_parent;
+ goto out_error;
}
nfs_advise_use_readdirplus(dir);
goto out_valid;
@@ -1144,8 +1146,10 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
trace_nfs_lookup_revalidate_enter(dir, dentry, flags);
error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr, label);
trace_nfs_lookup_revalidate_exit(dir, dentry, flags, error);
- if (error)
+ if (error == -ESTALE || error == -ENOENT)
goto out_bad;
+ if (error)
+ goto out_error;
if (nfs_compare_fh(NFS_FH(inode), fhandle))
goto out_bad;
if ((error = nfs_refresh_inode(inode, fattr)) != 0)
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 5751c1310177..7e7a894601b9 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1321,9 +1321,9 @@ static int nfs_check_inode_attributes(struct inode *inode, struct nfs_fattr *fat
return 0;
/* Has the inode gone and changed behind our back? */
if ((fattr->valid & NFS_ATTR_FATTR_FILEID) && nfsi->fileid != fattr->fileid)
- return -EIO;
+ return -ESTALE;
if ((fattr->valid & NFS_ATTR_FATTR_TYPE) && (inode->i_mode & S_IFMT) != (fattr->mode & S_IFMT))
- return -EIO;
+ return -ESTALE;
if (!nfs_file_has_buffered_writers(nfsi)) {
/* Verify a few of the more important attributes */
--
2.12.2
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