From 2c3ef4f89ced1a9d3a6fd4f6457be5c440c89362 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Mon, 20 Nov 2023 15:43:34 +0200 Subject: ovl: initialize ovl_copy_up_ctx.destname inside ovl_do_copy_up() The ->destname member of struct ovl_copy_up_ctx is initialized inside ovl_copy_up_one() to ->d_name of the overlayfs dentry being copied up and then it may be overridden by index name inside ovl_do_copy_up(). ovl_inode_lock() in ovl_copy_up_start() and ovl_copy_up() in ovl_rename() effectively stabilze ->d_name of the overlayfs dentry being copied up, but ovl_inode_lock() is not held when ->d_name is being read. It is not a correctness bug, because if ovl_do_copy_up() races with ovl_rename() and ctx.destname is freed, we will not end up calling ovl_do_copy_up() with the dead name reference. The code becomes much easier to understand and to document if the initialization of c->destname is always done inside ovl_do_copy_up(), either to the index entry name, or to the overlay dentry ->d_name. Signed-off-by: Amir Goldstein --- fs/overlayfs/copy_up.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'fs/overlayfs/copy_up.c') diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index 4382881b0709..500c555792ff 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -929,6 +929,13 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c) err = -EIO; goto out_free_fh; } else { + /* + * c->dentry->d_name is stabilzed by ovl_copy_up_start(), + * because if we got here, it means that c->dentry has no upper + * alias and changing ->d_name means going through ovl_rename() + * that will call ovl_copy_up() on source and target dentry. + */ + c->destname = c->dentry->d_name; /* * Mark parent "impure" because it may now contain non-pure * upper @@ -1109,7 +1116,6 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry, if (parent) { ovl_path_upper(parent, &parentpath); ctx.destdir = parentpath.dentry; - ctx.destname = dentry->d_name; err = vfs_getattr(&parentpath, &ctx.pstat, STATX_ATIME | STATX_MTIME, -- cgit v1.2.3