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pNFS: Fix a hang in nfs4_evict_inode()

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We are not allowed to call pnfs_mark_matching_lsegs_return() without
also holding a reference to the layout header, since doing so could lead
to the reference count going to zero when we call
pnfs_layout_remove_lseg(). This again can lead to a hang when we get to
nfs4_evict_inode() and are unable to clear the layout pointer.

pnfs_layout_return_unused_byserver() is guilty of this behaviour, and
has been seen to trigger the refcount warning prior to a hang.

Fixes: b6d49ecd10 ("NFSv4: Fix a pNFS layout related use-after-free race when freeing the inode")
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Trond Myklebust 2023-10-08 14:20:19 -04:00 committed by Anna Schumaker
parent 6a6d4644ce
commit f63955721a
1 changed files with 23 additions and 10 deletions
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33
fs/nfs/pnfs.c
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@ -2634,31 +2634,44 @@ pnfs_should_return_unused_layout(struct pnfs_layout_hdr *lo,
return mode == 0;
}
static int
pnfs_layout_return_unused_byserver(struct nfs_server *server, void *data)
static int pnfs_layout_return_unused_byserver(struct nfs_server *server,
void *data)
{
const struct pnfs_layout_range *range = data;
const struct cred *cred;
struct pnfs_layout_hdr *lo;
struct inode *inode;
nfs4_stateid stateid;
enum pnfs_iomode iomode;
restart:
rcu_read_lock();
list_for_each_entry_rcu(lo, &server->layouts, plh_layouts) {
if (!pnfs_layout_can_be_returned(lo) ||
inode = lo->plh_inode;
if (!inode || !pnfs_layout_can_be_returned(lo) ||
test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags))
continue;
inode = lo->plh_inode;
spin_lock(&inode->i_lock);
if (!pnfs_should_return_unused_layout(lo, range)) {
if (!lo->plh_inode ||
!pnfs_should_return_unused_layout(lo, range)) {
spin_unlock(&inode->i_lock);
continue;
}
pnfs_get_layout_hdr(lo);
pnfs_set_plh_return_info(lo, range->iomode, 0);
if (pnfs_mark_matching_lsegs_return(lo, &lo->plh_return_segs,
range, 0) != 0 ||
!pnfs_prepare_layoutreturn(lo, &stateid, &cred, &iomode)) {
spin_unlock(&inode->i_lock);
rcu_read_unlock();
pnfs_put_layout_hdr(lo);
cond_resched();
goto restart;
}
spin_unlock(&inode->i_lock);
inode = pnfs_grab_inode_layout_hdr(lo);
if (!inode)
continue;
rcu_read_unlock();
pnfs_mark_layout_for_return(inode, range);
iput(inode);
pnfs_send_layoutreturn(lo, &stateid, &cred, iomode, false);
pnfs_put_layout_hdr(lo);
cond_resched();
goto restart;
}