54a58185bf
Some drivers, for example, QCOM's qdf2xxx, set groups[gpio].name only when gpio is valid, and leave invalid gpio names as null. If we want to access the sys node "pinconf-groups", pinctrl_get_group_selector() -> get_group_name() may return a null pointer if group_selector is invalid, then the below Kernel panic would happen since strcmp() uses this null pointer to do comparison. Unable to handle kernel NULL pointer dereference at ss 00000000 el:Internal error: Oops: 9600000[ 143.080279] SMP CPU: 19 PID: 2493 Comm: read_all Tainted: G O .aarch64 #1 Hardware name: HXT Semiconductor HXT REP-2 System PC is at strcmp+0x18/0x154 LR is at pinctrl_get_group_selector+0x6c/0xe8 Process read_all (pid: 2493, stack limit = Call trace: Exception stack strcmp+0x18/0x154 pin_config_group_get+0x64/0xd8 pinconf_generic_dump_one+0xd8/0x1c0 pinconf_generic_dump_pins+0x94/0xc8 pinconf_groups_show+0xb4/0x104 seq_read+0x178/0x464 full_proxy_read+0x6c/0xac __vfs_read+0x58/0x178 vfs_read+0x94/0x164 SyS_read+0x60/0xc0 __sys_trace_return+0x0/0x4 --[ end trace]-- Kernel panic - not syncing: Fatal exception Signed-off-by: Yanjiang Jin <yanjiang.jin@hxt-semitech.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.