gpiolib: fix invalid pointer access in debugfs

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: gpiolib: fix invalid pointer access in debugfs If the memory allocation in gpiolib_seq_start() fails, the s->private field remains uninitialized and is later dereferenced without checking in gpiolib_seq_stop(). Initialize s->private to NULL before calling kzalloc() and check it before dereferencing it.

References

• https://git.kernel.org/stable/c/70180a6031056096c93ed2f47c41803268bdd91c
• https://git.kernel.org/stable/c/3c91c8f424d3e44c8645ab765a38773e58afb07d
• https://git.kernel.org/stable/c/2f6115ad8864cf3f48598f26c74c7c8e5c391919