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BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_DN_SOME(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_TLS_ALL(0.00)[]; MISSING_XM_UA(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCPT_COUNT_FIVE(0.00)[5]; RCVD_COUNT_TWO(0.00)[2]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[debian,bugreport]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email] X-Spam-Score: -2.80 X-Spam-Flag: NO dentry->d_fsdata is set to NFS_FSDATA_BLOCKED while unlinking or renaming-over a file to ensure that no open succeeds while the NFS operation progressed on the server. Setting dentry->d_fsdata to NFS_FSDATA_BLOCKED is done under ->d_lock after checking the refcount is not elevated. Any attempt to open the file (through that name) will go through lookp_open() which will take ->d_lock while incrementing the refcount, we can be sure that once the new value is set, __nfs_lookup_revalidate() *will* see the new value and will block. We don't have any locking guarantee that when we set ->d_fsdata to NULL, the wait_var_event() in __nfs_lookup_revalidate() will notice. wait/wake primitives do NOT provide barriers to guarantee order. We must use smp_load_acquire() in wait_var_event() to ensure we look at an up-to-date value, and must use smp_store_release() before wake_up_var(). This patch adds those barrier functions and factors out block_revalidate() and unblock_revalidate() far clarity. There is also a hypothetical bug in that if memory allocation fails (which never happens in practice) we might leave ->d_fsdata locked. This patch adds the missing call to unblock_revalidate(). Reported-and-tested-by: Richard Kojedzinszky Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1071501 Fixes: 3c59366c207e ("NFS: don't unhash dentry during unlink/rename") Signed-off-by: NeilBrown --- fs/nfs/dir.c | 44 +++++++++++++++++++++++++++++--------------- 1 file changed, 29 insertions(+), 15 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index ac505671efbd..c91dc36d41cc 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -1802,9 +1802,10 @@ __nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags, if (parent != READ_ONCE(dentry->d_parent)) return -ECHILD; } else { - /* Wait for unlink to complete */ + /* Wait for unlink to complete - see unblock_revalidate() */ wait_var_event(&dentry->d_fsdata, - dentry->d_fsdata != NFS_FSDATA_BLOCKED); + smp_load_acquire(&dentry->d_fsdata) + != NFS_FSDATA_BLOCKED); parent = dget_parent(dentry); ret = reval(d_inode(parent), dentry, flags); dput(parent); @@ -1817,6 +1818,26 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags) return __nfs_lookup_revalidate(dentry, flags, nfs_do_lookup_revalidate); } +static void block_revalidate(struct dentry *dentry) +{ + /* old devname - just in case */ + kfree(dentry->d_fsdata); + + /* Any new reference that could lead to an open + * will take ->d_lock in lookup_open() -> d_lookup(). + */ + lockdep_assert_held(&dentry->d_lock); + + dentry->d_fsdata = NULL; +} + +static void unblock_revalidate(struct dentry *dentry) +{ + /* store_release ensures wait_var_event() sees the update */ + smp_store_release(&dentry->d_fsdata, NULL); + wake_up_var(&dentry->d_fsdata); +} + /* * A weaker form of d_revalidate for revalidating just the d_inode(dentry) * when we don't really care about the dentry name. This is called when a @@ -2501,15 +2522,12 @@ int nfs_unlink(struct inode *dir, struct dentry *dentry) spin_unlock(&dentry->d_lock); goto out; } - /* old devname */ - kfree(dentry->d_fsdata); - dentry->d_fsdata = NFS_FSDATA_BLOCKED; + block_revalidate(dentry); spin_unlock(&dentry->d_lock); error = nfs_safe_remove(dentry); nfs_dentry_remove_handle_error(dir, dentry, error); - dentry->d_fsdata = NULL; - wake_up_var(&dentry->d_fsdata); + unblock_revalidate(dentry); out: trace_nfs_unlink_exit(dir, dentry, error); return error; @@ -2616,8 +2634,7 @@ nfs_unblock_rename(struct rpc_task *task, struct nfs_renamedata *data) { struct dentry *new_dentry = data->new_dentry; - new_dentry->d_fsdata = NULL; - wake_up_var(&new_dentry->d_fsdata); + unblock_revalidate(new_dentry); } /* @@ -2679,11 +2696,6 @@ int nfs_rename(struct mnt_idmap *idmap, struct inode *old_dir, if (WARN_ON(new_dentry->d_flags & DCACHE_NFSFS_RENAMED) || WARN_ON(new_dentry->d_fsdata == NFS_FSDATA_BLOCKED)) goto out; - if (new_dentry->d_fsdata) { - /* old devname */ - kfree(new_dentry->d_fsdata); - new_dentry->d_fsdata = NULL; - } spin_lock(&new_dentry->d_lock); if (d_count(new_dentry) > 2) { @@ -2705,7 +2717,7 @@ int nfs_rename(struct mnt_idmap *idmap, struct inode *old_dir, new_dentry = dentry; new_inode = NULL; } else { - new_dentry->d_fsdata = NFS_FSDATA_BLOCKED; + block_revalidate(new_dentry); must_unblock = true; spin_unlock(&new_dentry->d_lock); } @@ -2717,6 +2729,8 @@ int nfs_rename(struct mnt_idmap *idmap, struct inode *old_dir, task = nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry, must_unblock ? nfs_unblock_rename : NULL); if (IS_ERR(task)) { + if (must_unblock) + unblock_revalidate(new_dentry); error = PTR_ERR(task); goto out; }