From a3fbbde70a0cec017f2431e8f8de208708c76acc Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 7 Nov 2011 21:21:26 +0000 Subject: [PATCH] VFS: we need to set LOOKUP_JUMPED on mountpoint crossing Mountpoint crossing is similar to following procfs symlinks - we do not get ->d_revalidate() called for dentry we have arrived at, with unpleasant consequences for NFS4. Simple way to reproduce the problem in mainline: cat >/tmp/a.c <<'EOF' #include #include #include main() { struct flock fl = {.l_type = F_RDLCK, .l_whence = SEEK_SET, .l_len = 1}; if (fcntl(0, F_SETLK, &fl)) perror("setlk"); } EOF cc /tmp/a.c -o /tmp/test then on nfs4: mount --bind file1 file2 /tmp/test < file1 # ok /tmp/test < file2 # spews "setlk: No locks available"... What happens is the missing call of ->d_revalidate() after mountpoint crossing and that's where NFS4 would issue OPEN request to server. The fix is simple - treat mountpoint crossing the same way we deal with following procfs-style symlinks. I.e. set LOOKUP_JUMPED... Cc: stable@kernel.org Signed-off-by: Al Viro Signed-off-by: Linus Torvalds --- fs/namei.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/fs/namei.c b/fs/namei.c index ac6d214da827..5008f01787f5 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -852,7 +852,7 @@ static int follow_managed(struct path *path, unsigned flags) mntput(path->mnt); if (ret == -EISDIR) ret = 0; - return ret; + return ret < 0 ? ret : need_mntput; } int follow_down_one(struct path *path) @@ -900,6 +900,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, break; path->mnt = mounted; path->dentry = mounted->mnt_root; + nd->flags |= LOOKUP_JUMPED; nd->seq = read_seqcount_begin(&path->dentry->d_seq); /* * Update the inode too. We don't need to re-check the @@ -1213,6 +1214,8 @@ retry: path_put_conditional(path, nd); return err; } + if (err) + nd->flags |= LOOKUP_JUMPED; *inode = path->dentry->d_inode; return 0; } @@ -2146,6 +2149,10 @@ static struct file *do_last(struct nameidata *nd, struct path *path, } /* create side of things */ + /* + * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED has been + * cleared when we got to the last component we are about to look up + */ error = complete_walk(nd); if (error) return ERR_PTR(error); @@ -2214,6 +2221,9 @@ static struct file *do_last(struct nameidata *nd, struct path *path, if (error < 0) goto exit_dput; + if (error) + nd->flags |= LOOKUP_JUMPED; + error = -ENOENT; if (!path->dentry->d_inode) goto exit_dput; @@ -2223,6 +2233,10 @@ static struct file *do_last(struct nameidata *nd, struct path *path, path_to_nameidata(path, nd); nd->inode = path->dentry->d_inode; + /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ + error = complete_walk(nd); + if (error) + goto exit; error = -EISDIR; if (S_ISDIR(nd->inode->i_mode)) goto exit; -- 2.20.1