[android-common:android14-kiwi-6.1 390/390] kernel/trace/ring_buffer.c:2177 ring_buffer_resize() warn: variable dereferenced before check 'buffer' (see line 2172)

[Dan Carpenter <error27@gmail.com>]

tree:   https://android.googlesource.com/kernel/common android14-kiwi-6.1
head:   900d46d1c904d34d7c3eeb0ef2119cffc5a8ab3d
commit: 5ecbcb61e172d82faf1bd8c00b17837d3c658c59 [390/390] ANDROID: ring-buffer: Introducing external writer support
config: i386-randconfig-2200-20261105 (https://download.01.org/0day-ci/archive/20261105/202611051422.WODTXWDt-lkp@intel.com/config)
compiler: clang version 22.1.8 (https://github.com/llvm/llvm-project ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
smatch: v0.5.0-9187-g5189e3fb

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202611051422.WODTXWDt-lkp@intel.com/

smatch warnings:
kernel/trace/ring_buffer.c:2177 ring_buffer_resize() warn: variable dereferenced before check 'buffer' (see line 2172)

vim +/buffer +2177 kernel/trace/ring_buffer.c

13292494379f92 Steven Rostedt (VMware    2019-12-13  2165) int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
438ced1720b584 Vaibhav Nagarnaik         2012-02-02  2166  			int cpu_id)
7a8e76a3829f10 Steven Rostedt            2008-09-29  2167  {
7a8e76a3829f10 Steven Rostedt            2008-09-29  2168  	struct ring_buffer_per_cpu *cpu_buffer;
9b94a8fba501f3 Steven Rostedt (Red Hat   2016-05-12  2169) 	unsigned long nr_pages;
0a1754b2a97efa Qiujun Huang              2020-10-19  2170  	int cpu, err;
7a8e76a3829f10 Steven Rostedt            2008-09-29  2171  
5ecbcb61e172d8 Vincent Donnefort         2022-08-24 @2172  	if (unlikely(has_ext_writer(buffer)))
                                                                                            ^^^^^^
Unchecked dereference

5ecbcb61e172d8 Vincent Donnefort         2022-08-24  2173  		return -EINVAL;
ee51a1de7e3837 Ingo Molnar               2008-11-13  2174  	/*
ee51a1de7e3837 Ingo Molnar               2008-11-13  2175  	 * Always succeed at resizing a non-existent buffer:
ee51a1de7e3837 Ingo Molnar               2008-11-13  2176  	 */
ee51a1de7e3837 Ingo Molnar               2008-11-13 @2177  	if (!buffer)
                                                                    ^^^^^^^
Checked too late.

0a1754b2a97efa Qiujun Huang              2020-10-19  2178  		return 0;
ee51a1de7e3837 Ingo Molnar               2008-11-13  2179  
6a31e1f135d1ab Steven Rostedt            2012-05-23  2180  	/* Make sure the requested buffer exists */

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki