kernel/1246-proc-fix-missing-pde-set-flags-for-net-proc-files.patch

From 5b2ab6d1f5e5488a9faa61f4d560b239dce0e08b Mon Sep 17 00:00:00 2001
From: Abhi Das <adas@redhat.com>
Date: Fri, 17 Apr 2026 13:31:25 -0500
Subject: [PATCH] proc: fix missing pde_set_flags() for net proc files
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JIRA: https://redhat.atlassian.net/browse/RHEL-163346
CVE: CVE-2025-38653

commit 2ce3d282bd5050fca8577defeff08ada0d55d062
Author: wangzijie <wangzijie1@honor.com>
Date:   Mon Aug 18 20:31:02 2025 +0800

    proc: fix missing pde_set_flags() for net proc files

    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().

    [wangzijie1@honor.com: stash pde->proc_ops in a local const variable, per Christian]
      Link: https://lkml.kernel.org/r/20250821105806.1453833-1-wangzijie1@honor.com
    Link: https://lkml.kernel.org/r/20250818123102.959595-1-wangzijie1@honor.com
    Link: https://lore.kernel.org/all/20250815195616.64497967@chagall.paradoxon.rec/ [1]
    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>
    Tested-by: Stefano Brivio <sbrivio@redhat.com>
    Tested-by: Petr Vaněk <pv@excello.cz>
    Tested 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>

Signed-off-by: Abhi Das <adas@redhat.com>

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 26e118f1dc9e..88423b46e5ce 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -362,6 +362,25 @@ static const struct inode_operations proc_dir_inode_operations = {
 	.setattr	= proc_notify_change,
 };
 
+static void pde_set_flags(struct proc_dir_entry *pde)
+{
+	const struct proc_ops *proc_ops = pde->proc_ops;
+
+	if (!proc_ops)
+		return;
+
+	if (proc_ops->proc_flags & PROC_ENTRY_PERMANENT)
+		pde->flags |= PROC_ENTRY_PERMANENT;
+	if (proc_ops->proc_read_iter)
+		pde->flags |= PROC_ENTRY_proc_read_iter;
+#ifdef CONFIG_COMPAT
+	if (proc_ops->proc_compat_ioctl)
+		pde->flags |= PROC_ENTRY_proc_compat_ioctl;
+#endif
+	if (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)
@@ -369,6 +388,8 @@ struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
 	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) {
@@ -557,20 +578,6 @@ struct proc_dir_entry *proc_create_reg(const char *name, umode_t mode,
 	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)
@@ -581,7 +588,6 @@ struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
 	if (!p)
 		return NULL;
 	p->proc_ops = proc_ops;
-	pde_set_flags(p);
 	return proc_register(parent, p);
 }
 EXPORT_SYMBOL(proc_create_data);
@@ -632,7 +638,6 @@ struct proc_dir_entry *proc_create_seq_private(const char *name, umode_t mode,
 	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);
@@ -663,7 +668,6 @@ struct proc_dir_entry *proc_create_single_data(const char *name, umode_t mode,
 		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);
-- 
2.50.1 (Apple Git-155)