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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: ff7ec8dc1b ("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>
This commit is contained in:
wangzijie 2025-08-18 20:31:02 +08:00 committed by Andrew Morton
parent c3576889d8
commit 2ce3d282bd
1 changed files with 21 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
fs/proc/generic.c
View File

@ -367,6 +367,25 @@ 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)
@ -374,6 +393,8 @@ 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) {
@ -561,20 +582,6 @@ 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)
@ -585,7 +592,6 @@ 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);
@ -636,7 +642,6 @@ 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);
@ -667,7 +672,6 @@ 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);