6.6-stable review patch. If anyone has any objections, please let me know.
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From: wangzijie wangzijie1@honor.com
commit 2ce3d282bd5050fca8577defeff08ada0d55d062 upstream.
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: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/proc/generic.c | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-)
--- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -362,6 +362,25 @@ static const struct inode_operations pro .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(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) { @@ -557,20 +578,6 @@ 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) @@ -581,7 +588,6 @@ 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); @@ -632,7 +638,6 @@ 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); @@ -663,7 +668,6 @@ 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);