From f16857e62bac60786104c020ad7c86e2163b2c5b Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Fri, 19 Aug 2022 09:55:59 +1000 Subject: NFS: unlink/rmdir shouldn't call d_delete() twice on ENOENT nfs_unlink() calls d_delete() twice if it receives ENOENT from the server - once in nfs_dentry_handle_enoent() from nfs_safe_remove and once in nfs_dentry_remove_handle_error(). nfs_rmddir() also calls it twice - the nfs_dentry_handle_enoent() call is direct and inside a region locked with ->rmdir_sem It is safe to call d_delete() twice if the refcount > 1 as the dentry is simply unhashed. If the refcount is 1, the first call sets d_inode to NULL and the second call crashes. This patch guards the d_delete() call from nfs_dentry_handle_enoent() leaving the one under ->remdir_sem in case that is important. In mainline it would be safe to remove the d_delete() call. However in older kernels to which this might be backported, that would change the behaviour of nfs_unlink(). nfs_unlink() used to unhash the dentry which resulted in nfs_dentry_handle_enoent() not calling d_delete(). So in older kernels we need the d_delete() in nfs_dentry_remove_handle_error() when called from nfs_unlink() but not when called from nfs_rmdir(). To make the code work correctly for old and new kernels, and from both nfs_unlink() and nfs_rmdir(), we protect the d_delete() call with simple_positive(). This ensures it is never called in a circumstance where it could crash. Fixes: 3c59366c207e ("NFS: don't unhash dentry during unlink/rename") Fixes: 9019fb391de0 ("NFS: Label the dentry with a verifier in nfs_rmdir() and nfs_unlink()") Signed-off-by: NeilBrown Tested-by: Olga Kornievskaia Signed-off-by: Trond Myklebust --- fs/nfs/dir.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'fs/nfs/dir.c') diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 1b879584d4fe..5d6c2ddc7ea6 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -2382,7 +2382,8 @@ static void nfs_dentry_remove_handle_error(struct inode *dir, { switch (error) { case -ENOENT: - d_delete(dentry); + if (d_really_is_positive(dentry)) + d_delete(dentry); nfs_set_verifier(dentry, nfs_save_change_attribute(dir)); break; case 0: -- cgit v1.2.3-59-g8ed1b