From: Joel Stanley Date: Thu, 24 Apr 2014 07:25:33 +0000 (+0930) Subject: powerpc/powernv: Fix sysparam sysfs error handling X-Git-Tag: firefly_0821_release~176^2~3843^2~35 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=ba9a32b176c31ec4d3d7314bb2e529a85423f7a4;p=firefly-linux-kernel-4.4.55.git powerpc/powernv: Fix sysparam sysfs error handling When a sysparam query in OPAL returned a negative value (error code), sysfs would spew out a decent chunk of memory; almost 64K more than expected. This was traced to a sign/unsigned mix up in the OPAL sysparam sysfs code at sys_param_show. The return value of sys_param_show is a ssize_t, calculated using return ret ? ret : attr->param_size; Alan Modra explains: "attr->param_size" is an unsigned int, "ret" an int, so the overall expression has type unsigned int. Result is that ret is cast to unsigned int before being cast to ssize_t. Instead of using the ternary operator, set ret to the param_size if an error is not detected. The same bug exists in the sysfs write callback; this patch fixes it in the same way. A note on debugging this next time: on my system gcc will warn about this if compiled with -Wsign-compare, which is not enabled by -Wall, only -Wextra. Signed-off-by: Joel Stanley Signed-off-by: Benjamin Herrenschmidt --- diff --git a/arch/powerpc/platforms/powernv/opal-sysparam.c b/arch/powerpc/platforms/powernv/opal-sysparam.c index 6b614726baf2..a51ea189aec3 100644 --- a/arch/powerpc/platforms/powernv/opal-sysparam.c +++ b/arch/powerpc/platforms/powernv/opal-sysparam.c @@ -121,9 +121,10 @@ static ssize_t sys_param_show(struct kobject *kobj, memcpy(buf, param_data_buf, attr->param_size); + ret = attr->param_size; out: mutex_unlock(&opal_sysparam_mutex); - return ret ? ret : attr->param_size; + return ret; } static ssize_t sys_param_store(struct kobject *kobj, @@ -138,7 +139,9 @@ static ssize_t sys_param_store(struct kobject *kobj, ret = opal_set_sys_param(attr->param_id, attr->param_size, param_data_buf); mutex_unlock(&opal_sysparam_mutex); - return ret ? ret : count; + if (!ret) + ret = count; + return ret; } void __init opal_sys_param_init(void)