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().
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