+ proc-fix-missing-pde_set_flags-for-net-proc-files.patch added to mm-hotfixes-unstable branch

+ proc-fix-missing-pde_set_flags-for-net-proc-files.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: proc: fix missing pde_set_flags() for net proc files
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     proc-fix-missing-pde_set_flags-for-net-proc-files.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/proc-fix-missing-pde_set_flags-for-net-proc-files.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: wangzijie <wangzijie1@honor.com>
Subject: proc: fix missing pde_set_flags() for net proc files
Date: Mon, 18 Aug 2025 20:31:02 +0800

To avoid potential UAF issues during module removal races, we use
pde_set_flags() to save proc_ops flags in PDE itself before
proc_register(), and then use pde_has_proc_*() helpers instead of directly
dereferencing pde->proc_ops->*.

However, the pde_set_flags() call was missing when creating net related
proc files.  This omission caused incorrect behavior which FMODE_LSEEK was
being cleared inappropriately in proc_reg_open() for net proc files.  Lars
reported it in this link[1].

Fix this by ensuring pde_set_flags() is called when register proc entry,
and add NULL check for proc_ops in pde_set_flags().

[1]: https://lore.kernel.org/all/20250815195616.64497967@chagall.paradoxon.rec/

Link: https://lkml.kernel.org/r/20250818123102.959595-1-wangzijie1@honor.com
Fixes: ff7ec8dc1b64 ("proc: use the same treatment to check proc_lseek as ones for proc_read_iter et.al)
Signed-off-by: wangzijie <wangzijie1@honor.com>
Reported-by: Lars Wendler <polynomial-c@gmx.de>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Kirill A. Shutemov <k.shutemov@gmail.com>
Cc: wangzijie <wangzijie1@honor.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/generic.c |   36 +++++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 17 deletions(-)

--- a/fs/proc/generic.c~proc-fix-missing-pde_set_flags-for-net-proc-files
+++ a/fs/proc/generic.c
@@ -367,6 +367,23 @@ static const struct inode_operations pro
 	.setattr	= proc_notify_change,
 };
 
+static void pde_set_flags(struct proc_dir_entry *pde)
+{
+	if (!pde->proc_ops)
+		return;
+
+	if (pde->proc_ops->proc_flags & PROC_ENTRY_PERMANENT)
+		pde->flags |= PROC_ENTRY_PERMANENT;
+	if (pde->proc_ops->proc_read_iter)
+		pde->flags |= PROC_ENTRY_proc_read_iter;
+#ifdef CONFIG_COMPAT
+	if (pde->proc_ops->proc_compat_ioctl)
+		pde->flags |= PROC_ENTRY_proc_compat_ioctl;
+#endif
+	if (pde->proc_ops->proc_lseek)
+		pde->flags |= PROC_ENTRY_proc_lseek;
+}
+
 /* returns the registered entry, or frees dp and returns NULL on failure */
 struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
 		struct proc_dir_entry *dp)
@@ -374,6 +391,8 @@ struct proc_dir_entry *proc_register(str
 	if (proc_alloc_inum(&dp->low_ino))
 		goto out_free_entry;
 
+	pde_set_flags(dp);
+
 	write_lock(&proc_subdir_lock);
 	dp->parent = dir;
 	if (pde_subdir_insert(dir, dp) == false) {
@@ -561,20 +580,6 @@ struct proc_dir_entry *proc_create_reg(c
 	return p;
 }
 
-static void pde_set_flags(struct proc_dir_entry *pde)
-{
-	if (pde->proc_ops->proc_flags & PROC_ENTRY_PERMANENT)
-		pde->flags |= PROC_ENTRY_PERMANENT;
-	if (pde->proc_ops->proc_read_iter)
-		pde->flags |= PROC_ENTRY_proc_read_iter;
-#ifdef CONFIG_COMPAT
-	if (pde->proc_ops->proc_compat_ioctl)
-		pde->flags |= PROC_ENTRY_proc_compat_ioctl;
-#endif
-	if (pde->proc_ops->proc_lseek)
-		pde->flags |= PROC_ENTRY_proc_lseek;
-}
-
 struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
 		struct proc_dir_entry *parent,
 		const struct proc_ops *proc_ops, void *data)
@@ -585,7 +590,6 @@ struct proc_dir_entry *proc_create_data(
 	if (!p)
 		return NULL;
 	p->proc_ops = proc_ops;
-	pde_set_flags(p);
 	return proc_register(parent, p);
 }
 EXPORT_SYMBOL(proc_create_data);
@@ -636,7 +640,6 @@ struct proc_dir_entry *proc_create_seq_p
 	p->proc_ops = &proc_seq_ops;
 	p->seq_ops = ops;
 	p->state_size = state_size;
-	pde_set_flags(p);
 	return proc_register(parent, p);
 }
 EXPORT_SYMBOL(proc_create_seq_private);
@@ -667,7 +670,6 @@ struct proc_dir_entry *proc_create_singl
 		return NULL;
 	p->proc_ops = &proc_single_ops;
 	p->single_show = show;
-	pde_set_flags(p);
 	return proc_register(parent, p);
 }
 EXPORT_SYMBOL(proc_create_single_data);
_

Patches currently in -mm which might be from wangzijie1@honor.com are

proc-fix-missing-pde_set_flags-for-net-proc-files.patch