Re: [PATCH v3] proc: fix missing pde_set_flags() for net proc files

[Lars Wendler <polynomial-c@gmx.de>]

Am Sun, 24 Aug 2025 11:00:55 +0200
schrieb Petr Vaněk <pv@excello.cz>:

> On Thu, Aug 21, 2025 at 06:58:06PM +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") Cc:
> > stable@vger.kernel.org Reported-by: Lars Wendler
> > <polynomial-c@gmx.de> Signed-off-by: wangzijie
> > <wangzijie1@honor.com>
> 
> Tested-by: Petr Vaněk <pv@excello.cz>
> 
> We have noticed lseek issue with /proc/self/net/sockstat file recently
> and this patch fixes it for us.
> 
> Thanks,
> Petr

Applied to linux-6.12.43 and it fixes the issue in linux-6.12.y branch.
I have yet to test it in linux-6.6.y branch.

Tested by: Lars Wendler <polynomial-c@gmx.de>

Thanks
Lars