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@@ -1,121 +0,0 @@
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From: wangzijie <wangzijie1@honor.com>
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To: <akpm@linux-foundation.org>, <brauner@kernel.org>,
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<viro@zeniv.linux.org.uk>, <adobriyan@gmail.com>,
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<rick.p.edgecombe@intel.com>, <ast@kernel.org>,
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<k.shutemov@gmail.com>, <jirislaby@kernel.org>,
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<linux-fsdevel@vger.kernel.org>
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Cc: <polynomial-c@gmx.de>, <gregkh@linuxfoundation.org>,
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<stable@vger.kernel.org>, <regressions@lists.linux.dev>,
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wangzijie <wangzijie1@honor.com>
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Subject: [PATCH v3] proc: fix missing pde_set_flags() for net proc files
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Date: Thu, 21 Aug 2025 18:58:06 +0800 [thread overview]
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Message-ID: <20250821105806.1453833-1-wangzijie1@honor.com> (raw)
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To avoid potential UAF issues during module removal races, we use pde_set_flags()
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to save proc_ops flags in PDE itself before proc_register(), and then use
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pde_has_proc_*() helpers instead of directly dereferencing pde->proc_ops->*.
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However, the pde_set_flags() call was missing when creating net related proc files.
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This omission caused incorrect behavior which FMODE_LSEEK was being cleared
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inappropriately in proc_reg_open() for net proc files. Lars reported it in this link[1].
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Fix this by ensuring pde_set_flags() is called when register proc entry, and add
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NULL check for proc_ops in pde_set_flags().
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[1]: https://lore.kernel.org/all/20250815195616.64497967@chagall.paradoxon.rec/
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Fixes: ff7ec8dc1b64 ("proc: use the same treatment to check proc_lseek as ones for proc_read_iter et.al")
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Cc: stable@vger.kernel.org
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Reported-by: Lars Wendler <polynomial-c@gmx.de>
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Signed-off-by: wangzijie <wangzijie1@honor.com>
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---
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v3:
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- followed by Christian's suggestion to stash pde->proc_ops in a local const variable
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v2:
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- followed by Jiri's suggestion to refractor code and reformat commit message
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---
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fs/proc/generic.c | 38 +++++++++++++++++++++-----------------
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1 file changed, 21 insertions(+), 17 deletions(-)
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--- a/fs/proc/generic.c
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+++ b/fs/proc/generic.c
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@@ -362,6 +362,25 @@ static const struct inode_operations pro
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.setattr = proc_notify_change,
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};
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+static void pde_set_flags(struct proc_dir_entry *pde)
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+{
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+ const struct proc_ops *proc_ops = pde->proc_ops;
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+
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+ if (!proc_ops)
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+ return;
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+
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+ if (proc_ops->proc_flags & PROC_ENTRY_PERMANENT)
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+ pde->flags |= PROC_ENTRY_PERMANENT;
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+ if (proc_ops->proc_read_iter)
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+ pde->flags |= PROC_ENTRY_proc_read_iter;
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+#ifdef CONFIG_COMPAT
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+ if (proc_ops->proc_compat_ioctl)
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+ pde->flags |= PROC_ENTRY_proc_compat_ioctl;
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+#endif
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+ if (proc_ops->proc_lseek)
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+ pde->flags |= PROC_ENTRY_proc_lseek;
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+}
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+
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/* returns the registered entry, or frees dp and returns NULL on failure */
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struct proc_dir_entry *proc_register(struct proc_dir_entry *dir,
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struct proc_dir_entry *dp)
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@@ -369,6 +388,8 @@ struct proc_dir_entry *proc_register(str
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if (proc_alloc_inum(&dp->low_ino))
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goto out_free_entry;
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+ pde_set_flags(dp);
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+
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write_lock(&proc_subdir_lock);
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dp->parent = dir;
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if (pde_subdir_insert(dir, dp) == false) {
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@@ -557,20 +578,6 @@ struct proc_dir_entry *proc_create_reg(c
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return p;
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}
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-static void pde_set_flags(struct proc_dir_entry *pde)
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-{
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- if (pde->proc_ops->proc_flags & PROC_ENTRY_PERMANENT)
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- pde->flags |= PROC_ENTRY_PERMANENT;
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- if (pde->proc_ops->proc_read_iter)
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- pde->flags |= PROC_ENTRY_proc_read_iter;
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-#ifdef CONFIG_COMPAT
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- if (pde->proc_ops->proc_compat_ioctl)
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- pde->flags |= PROC_ENTRY_proc_compat_ioctl;
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-#endif
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- if (pde->proc_ops->proc_lseek)
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- pde->flags |= PROC_ENTRY_proc_lseek;
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-}
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-
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struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
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struct proc_dir_entry *parent,
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const struct proc_ops *proc_ops, void *data)
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@@ -581,7 +588,6 @@ struct proc_dir_entry *proc_create_data(
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if (!p)
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return NULL;
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p->proc_ops = proc_ops;
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- pde_set_flags(p);
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return proc_register(parent, p);
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}
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EXPORT_SYMBOL(proc_create_data);
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@@ -632,7 +638,6 @@ struct proc_dir_entry *proc_create_seq_p
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p->proc_ops = &proc_seq_ops;
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p->seq_ops = ops;
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p->state_size = state_size;
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- pde_set_flags(p);
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return proc_register(parent, p);
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}
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EXPORT_SYMBOL(proc_create_seq_private);
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@@ -663,7 +668,6 @@ struct proc_dir_entry *proc_create_singl
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return NULL;
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p->proc_ops = &proc_single_ops;
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p->single_show = show;
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- pde_set_flags(p);
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return proc_register(parent, p);
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}
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EXPORT_SYMBOL(proc_create_single_data);
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