Re: [PATCH v2] proc: fix missing pde_set_flags() for net proc files

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Aug 18, 2025 at 07:24:28PM +0800, wangzijie wrote:
> 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/
> 
> Fixes: ff7ec8dc1b64 ("proc: use the same treatment to check proc_lseek as ones for proc_read_iter et.al)
> Reported-by: Lars Wendler <polynomial-c@gmx.de>
> Signed-off-by: wangzijie <wangzijie1@honor.com>
> ---
> v2:
> - followed by Jiri's suggestion to refractor code and reformat commit message
> ---
>  fs/proc/generic.c | 36 +++++++++++++++++++-----------------
>  1 file changed, 19 insertions(+), 17 deletions(-)
> 


<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>