From d3160e70e443250fea4df3cb6fea7c217f03e97e Mon Sep 17 00:00:00 2001 From: Nirmoy Das Date: Thu, 14 May 2026 07:42:57 -0700 Subject: [PATCH] ovl: keep err zero after successful ovl_cache_get() ovl_iterate_merged() stores PTR_ERR(cache) in err before checking IS_ERR(cache). On success err holds the truncated cache pointer and can be returned as a bogus non-zero error. The syzbot reproducer reaches this through overlay-on-overlay readdir: getdents64 iterate_dir(outer overlay file) ovl_iterate_merged() ovl_cache_get() ovl_dir_read_merged() ovl_dir_read() iterate_dir(inner overlay file) ovl_iterate_merged() Only compute PTR_ERR(cache) on the error path. Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard") Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c Cc: stable@vger.kernel.org Signed-off-by: Nirmoy Das Link: https://patch.msgid.link/20260514144258.3068715-1-nirmoyd@nvidia.com Signed-off-by: Christian Brauner (cherry picked from commit 1711b6ed6953cee5940ca4c3a6e77f1b3798cee2) Signed-off-by: Chia-Lin Kao (AceLan) --- fs/overlayfs/readdir.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c index 1dcc75b3a90f9..e7fe29cb6028b 100644 --- a/fs/overlayfs/readdir.c +++ b/fs/overlayfs/readdir.c @@ -838,15 +838,14 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) struct ovl_dir_file *od = file->private_data; struct dentry *dentry = file->f_path.dentry; struct ovl_cache_entry *p; - int err = 0; + int err; if (!od->cache) { struct ovl_dir_cache *cache; cache = ovl_cache_get(dentry); - err = PTR_ERR(cache); if (IS_ERR(cache)) - return err; + return PTR_ERR(cache); od->cache = cache; ovl_seek_cursor(od, ctx->pos); @@ -869,7 +868,7 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) od->cursor = p->l_node.next; ctx->pos++; } - return err; + return 0; } static bool ovl_need_adjust_d_ino(struct file *file) -- 2.53.0