[PATCH 5.10 45/63] NFSv4: Fix a pNFS layout related use-after-free race when freeing the inode

Greg Kroah-Hartman
2021-01-04T16:06:20Z

From: Trond Myklebust <trond.myklebust@hammerspace.com>

[ Upstream commit b6d49ecd1081740b6e632366428b960461f8158b ]

When returning the layout in nfs4_evict_inode(), we need to ensure that
the layout is actually done being freed before we can proceed to free the
inode itself.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfs/nfs4super.c | 2 +-
fs/nfs/pnfs.c | 33 +++++++++++++++++++++++++++++++--
fs/nfs/pnfs.h | 5 +++++
3 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs4super.c b/fs/nfs/nfs4super.c
index 93f5c1678ec29..984cc42ee54d8 100644
--- a/fs/nfs/nfs4super.c
+++ b/fs/nfs/nfs4super.c
@@ -67,7 +67,7 @@ static void nfs4_evict_inode(struct inode *inode)
nfs_inode_evict_delegation(inode);
/* Note that above delegreturn would trigger pnfs return-on-close */
pnfs_return_layout(inode);
- pnfs_destroy_layout(NFS_I(inode));
+ pnfs_destroy_layout_final(NFS_I(inode));
/* First call standard NFS clear_inode() code */
nfs_clear_inode(inode);
nfs4_xattr_cache_zap(inode);
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 0e50b9d45c320..07f59dc8cb2e7 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -294,6 +294,7 @@ void
pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo)
{
struct inode *inode;
+ unsigned long i_state;

if (!lo)
return;
@@ -304,8 +305,12 @@ pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo)
if (!list_empty(&lo->plh_segs))
WARN_ONCE(1, "NFS: BUG unfreed layout segments.\n");
pnfs_detach_layout_hdr(lo);
+ i_state = inode->i_state;
spin_unlock(&inode->i_lock);
pnfs_free_layout_hdr(lo);
+ /* Notify pnfs_destroy_layout_final() that we're done */
+ if (i_state & (I_FREEING | I_CLEAR))
+ wake_up_var(lo);
}
}

@@ -734,8 +739,7 @@ pnfs_free_lseg_list(struct list_head *free_me)
}
}

-void
-pnfs_destroy_layout(struct nfs_inode *nfsi)
+static struct pnfs_layout_hdr *__pnfs_destroy_layout(struct nfs_inode *nfsi)
{
struct pnfs_layout_hdr *lo;
LIST_HEAD(tmp_list);
@@ -753,9 +757,34 @@ pnfs_destroy_layout(struct nfs_inode *nfsi)
pnfs_put_layout_hdr(lo);
} else
spin_unlock(&nfsi->vfs_inode.i_lock);
+ return lo;
+}
+
+void pnfs_destroy_layout(struct nfs_inode *nfsi)
+{
+ __pnfs_destroy_layout(nfsi);
}
EXPORT_SYMBOL_GPL(pnfs_destroy_layout);

+static bool pnfs_layout_removed(struct nfs_inode *nfsi,
+ struct pnfs_layout_hdr *lo)
+{
+ bool ret;
+
+ spin_lock(&nfsi->vfs_inode.i_lock);
+ ret = nfsi->layout != lo;
+ spin_unlock(&nfsi->vfs_inode.i_lock);
+ return ret;
+}
+
+void pnfs_destroy_layout_final(struct nfs_inode *nfsi)
+{
+ struct pnfs_layout_hdr *lo = __pnfs_destroy_layout(nfsi);
+
+ if (lo)
+ wait_var_event(lo, pnfs_layout_removed(nfsi, lo));
+}
+
static bool
pnfs_layout_add_bulk_destroy_list(struct inode *inode,
struct list_head *layout_list)
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 2661c44c62db4..78c3893918486 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -266,6 +266,7 @@ struct pnfs_layout_segment *pnfs_layout_process(struct nfs4_layoutget *lgp);
void pnfs_layoutget_free(struct nfs4_layoutget *lgp);
void pnfs_free_lseg_list(struct list_head *tmp_list);
void pnfs_destroy_layout(struct nfs_inode *);
+void pnfs_destroy_layout_final(struct nfs_inode *);
void pnfs_destroy_all_layouts(struct nfs_client *);
int pnfs_destroy_layouts_byfsid(struct nfs_client *clp,
struct nfs_fsid *fsid,
@@ -710,6 +711,10 @@ static inline void pnfs_destroy_layout(struct nfs_inode *nfsi)
{
}

+static inline void pnfs_destroy_layout_final(struct nfs_inode *nfsi)
+{
+}
+
static inline struct pnfs_layout_segment *
pnfs_get_lseg(struct pnfs_layout_segment *lseg)
{
--
2.27.0