| Message ID | 1510042169-16664-1-git-send-email-ego@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Rafael Wysocki |
| Headers | show |
On 07-11-17, 13:39, Gautham R. Shenoy wrote: > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> > > On platforms with large number of Pstates, the transition table, which > is a NxN matrix, can overflow beyond the PAGE_SIZE boundary. > > This can be seen on POWER9 which has 100+ Pstates. > > As a result, each time the trans_table is read for any of the CPUs, we > will get the following error. > > --------------------------------------------------- > fill_read_buffer: show+0x0/0xa0 returned bad count > --------------------------------------------------- > > This patch ensures that in case of an overflow, we print a warning > once in the dmesg and return FILE TOO LARGE error for this and all > subsequent accesses of trans_table. > > Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> > --- > Documentation/cpu-freq/cpufreq-stats.txt | 3 +++ > drivers/cpufreq/cpufreq_stats.c | 7 +++++-- > 2 files changed, 8 insertions(+), 2 deletions(-) Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
diff --git a/Documentation/cpu-freq/cpufreq-stats.txt b/Documentation/cpu-freq/cpufreq-stats.txt index 2bbe207..a873855 100644 --- a/Documentation/cpu-freq/cpufreq-stats.txt +++ b/Documentation/cpu-freq/cpufreq-stats.txt @@ -90,6 +90,9 @@ Freq_i to Freq_j. Freq_i is in descending order with increasing rows and Freq_j is in descending order with increasing columns. The output here also contains the actual freq values for each row and column for better readability. +If the transition table is bigger than PAGE_SIZE, reading this will +return an -EFBIG error. + -------------------------------------------------------------------------------- <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat trans_table From : To diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c index e75880e..1e55b57 100644 --- a/drivers/cpufreq/cpufreq_stats.c +++ b/drivers/cpufreq/cpufreq_stats.c @@ -118,8 +118,11 @@ static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf) break; len += snprintf(buf + len, PAGE_SIZE - len, "\n"); } - if (len >= PAGE_SIZE) - return PAGE_SIZE; + + if (len >= PAGE_SIZE) { + pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n"); + return -EFBIG; + } return len; } cpufreq_freq_attr_ro(trans_table);