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NFS: nfs_delegation_find_inode_server must first reference the superblock 

Before referencing the inode, we must ensure that the superblock can be
referenced. Otherwise, we can end up with iput() calling superblock
operations that are no longer valid or accessible.

Fixes: e39d8a186e ("NFSv4: Fix an Oops during delegation callbacks")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
master
Trond Myklebust 2021-01-10 15:46:06 -05:00
parent cb2856c597
commit 113aac6d56
1 changed files with 7 additions and 5 deletions
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12
fs/nfs/delegation.c
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@ -1011,22 +1011,24 @@ nfs_delegation_find_inode_server(struct nfs_server *server,
const struct nfs_fh *fhandle)
{
struct nfs_delegation *delegation;
struct inode *freeme, *res = NULL;
struct super_block *freeme = NULL;
struct inode *res = NULL;
list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
spin_lock(&delegation->lock);
if (delegation->inode != NULL &&
!test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
nfs_compare_fh(fhandle, &NFS_I(delegation->inode)->fh) == 0) {
freeme = igrab(delegation->inode);
if (freeme && nfs_sb_active(freeme->i_sb))
res = freeme;
if (nfs_sb_active(server->super)) {
freeme = server->super;
res = igrab(delegation->inode);
}
spin_unlock(&delegation->lock);
if (res != NULL)
return res;
if (freeme) {
rcu_read_unlock();
iput(freeme);
nfs_sb_deactive(freeme);
rcu_read_lock();
}
return ERR_PTR(-EAGAIN);