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cpufreq: amd-pstate: avoid uninitialized variable use 

The new epp support causes warnings about three separate
but related bugs:

1) failing before allocation should just return an error:

drivers/cpufreq/amd-pstate.c:951:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
        if (!dev)
            ^~~~
drivers/cpufreq/amd-pstate.c:1018:9: note: uninitialized use occurs here
        return ret;
               ^~~

2) wrong variable to store return code:

drivers/cpufreq/amd-pstate.c:963:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
        if (rc)
            ^~
drivers/cpufreq/amd-pstate.c:1019:9: note: uninitialized use occurs here
        return ret;
               ^~~
drivers/cpufreq/amd-pstate.c:963:2: note: remove the 'if' if its condition is always false
        if (rc)
        ^~~~~~~

3) calling amd_pstate_set_epp() in cleanup path after determining
that it should not be called:

drivers/cpufreq/amd-pstate.c:1055:6: error: variable 'epp' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
        if (cpudata->epp_policy == cpudata->policy)
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/cpufreq/amd-pstate.c:1080:30: note: uninitialized use occurs here
        amd_pstate_set_epp(cpudata, epp);
                                    ^~~

All three are trivial to fix, but most likely there are additional bugs
in this function when the error handling was not really tested.

Fixes: ffa5096a7c ("cpufreq: amd-pstate: implement Pstate EPP support for the AMD processors")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Wyes Karny <wyes.karny@amd.com>
Reviewed-by: Yuan Perry <Perry.Yuan@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Arnd Bergmann 2023-02-07 17:12:51 +01:00 committed by Rafael J. Wysocki
parent dd329e1e21
commit 7cca9a9851
1 changed files with 4 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/cpufreq/amd-pstate.c
View File

@ -940,7 +940,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;
struct amd_cpudata *cpudata;
struct device *dev;
int rc;
u64 value;
/*
@ -950,7 +949,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
amd_perf_ctl_reset(policy->cpu);
dev = get_cpu_device(policy->cpu);
if (!dev)
goto free_cpudata1;
return -ENODEV;
cpudata = kzalloc(sizeof(*cpudata), GFP_KERNEL);
if (!cpudata)
@ -959,8 +958,8 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
cpudata->cpu = policy->cpu;
cpudata->epp_policy = 0;
rc = amd_pstate_init_perf(cpudata);
if (rc)
ret = amd_pstate_init_perf(cpudata);
if (ret)
goto free_cpudata1;
min_freq = amd_get_min_freq(cpudata);
@ -1076,9 +1075,9 @@ static void amd_pstate_epp_init(unsigned int cpu)
value |= (u64)epp << 24;
}
amd_pstate_set_epp(cpudata, epp);
skip_epp:
WRITE_ONCE(cpudata->cppc_req_cached, value);
amd_pstate_set_epp(cpudata, epp);
cpufreq_cpu_put(policy);
}