From 25d72077215cdec3b5eb884c7c363d2714ac2725 Mon Sep 17 00:00:00 2001
From: Abhishek Mishra <mishra.abhishek2808@gmail.com>
Date: Wed, 20 May 2026 07:53:18 +0000
Subject: [PATCH] fs/vfs: validate chmod and chown callers in inode_chstat()

Add pseudoFS caller validation for chmod and chown operations
using the caller's effective uid. Align behavior with POSIX
semantics by allowing owner/root chmod and root-only chown.

Signed-off-by: Abhishek Mishra <mishra.abhishek2808@gmail.com>
---
 fs/vfs/fs_chstat.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/fs/vfs/fs_chstat.c b/fs/vfs/fs_chstat.c
index 9b0c50c3933..1d1828992f5 100644
--- a/fs/vfs/fs_chstat.c
+++ b/fs/vfs/fs_chstat.c
@@ -32,6 +32,7 @@
 #include <errno.h>
 
 #include <nuttx/fs/fs.h>
+#include <nuttx/sched.h>
 
 #include "inode/inode.h"
 
@@ -410,6 +411,11 @@ int lutimens(FAR const char *path, const struct timespec times[2])
 int inode_chstat(FAR struct inode *inode,
                  FAR const struct stat *buf, int flags, int resolve)
 {
+#ifdef CONFIG_SCHED_USER_IDENTITY
+  FAR struct tcb_s *rtcb;
+  uid_t euid;
+#endif
+
   DEBUGASSERT(inode != NULL && buf != NULL);
 
 #ifdef CONFIG_PSEUDOFS_SOFTLINKS
@@ -443,6 +449,28 @@ int inode_chstat(FAR struct inode *inode,
     }
 #endif
 
+#ifdef CONFIG_SCHED_USER_IDENTITY
+  rtcb = nxsched_self();
+  if ((rtcb->flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_KERNEL &&
+      rtcb->group != NULL)
+    {
+      euid = rtcb->group->tg_euid;
+
+      if ((flags & (CH_STAT_UID | CH_STAT_GID)) != 0 && euid != 0)
+        {
+          return -EPERM;
+        }
+
+#ifdef CONFIG_PSEUDOFS_ATTRIBUTES
+      if ((flags & CH_STAT_MODE) != 0 &&
+          euid != 0 && euid != inode->i_owner)
+        {
+          return -EPERM;
+        }
+#endif
+    }
+#endif
+
 #ifdef CONFIG_PSEUDOFS_ATTRIBUTES
   if (flags & CH_STAT_MODE)
     {