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s390/stp: add locking to sysfs functions
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commit b3bd024 upstream.

The sysfs function might race with stp_work_fn. To prevent that,
add the required locking. Another issue is that the sysfs functions
are checking the stp_online flag, but this flag just holds the user
setting whether STP is enabled. Add a flag to clock_sync_flag whether
stp_info holds valid data and use that instead.

Cc: stable@vger.kernel.org
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@svens-s390 @gregkh
svens-s390 authored and gregkh committed Nov 5, 2020
1 parent 58a7dc5 commit 551bf7c
Showing 1 changed file with 85 additions and 33 deletions.
118 changes: 85 additions & 33 deletions arch/s390/kernel/time.c
View file
Expand Up @@ -354,8 +354,9 @@ static DEFINE_PER_CPU(atomic_t, clock_sync_word);
static DEFINE_MUTEX(clock_sync_mutex);
static unsigned long clock_sync_flags;

#define CLOCK_SYNC_HAS_STP 0
#define CLOCK_SYNC_STP 1
#define CLOCK_SYNC_HAS_STP 0
#define CLOCK_SYNC_STP 1
#define CLOCK_SYNC_STPINFO_VALID 2

/*
* The get_clock function for the physical clock. It will get the current
Expand Down Expand Up @@ -592,6 +593,22 @@ void stp_queue_work(void)
queue_work(time_sync_wq, &stp_work);
}

static int __store_stpinfo(void)
{
int rc = chsc_sstpi(stp_page, &stp_info, sizeof(struct stp_sstpi));

if (rc)
clear_bit(CLOCK_SYNC_STPINFO_VALID, &clock_sync_flags);
else
set_bit(CLOCK_SYNC_STPINFO_VALID, &clock_sync_flags);
return rc;
}

static int stpinfo_valid(void)
{
return stp_online && test_bit(CLOCK_SYNC_STPINFO_VALID, &clock_sync_flags);
}

static int stp_sync_clock(void *data)
{
struct clock_sync_data *sync = data;
Expand All @@ -613,8 +630,7 @@ static int stp_sync_clock(void *data)
if (rc == 0) {
sync->clock_delta = clock_delta;
clock_sync_global(clock_delta);
rc = chsc_sstpi(stp_page, &stp_info,
sizeof(struct stp_sstpi));
rc = __store_stpinfo();
if (rc == 0 && stp_info.tmd != 2)
rc = -EAGAIN;
}
Expand Down Expand Up @@ -659,7 +675,7 @@ static void stp_work_fn(struct work_struct *work)
if (rc)
goto out_unlock;

rc = chsc_sstpi(stp_page, &stp_info, sizeof(struct stp_sstpi));
rc = __store_stpinfo();
if (rc || stp_info.c == 0)
goto out_unlock;

Expand Down Expand Up @@ -696,10 +712,14 @@ static ssize_t stp_ctn_id_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
if (!stp_online)
return -ENODATA;
return sprintf(buf, "%016llx\n",
*(unsigned long long *) stp_info.ctnid);
ssize_t ret = -ENODATA;

mutex_lock(&stp_work_mutex);
if (stpinfo_valid())
ret = sprintf(buf, "%016llx\n",
*(unsigned long long *) stp_info.ctnid);
mutex_unlock(&stp_work_mutex);
return ret;
}

static DEVICE_ATTR(ctn_id, 0400, stp_ctn_id_show, NULL);
Expand All @@ -708,9 +728,13 @@ static ssize_t stp_ctn_type_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
if (!stp_online)
return -ENODATA;
return sprintf(buf, "%i\n", stp_info.ctn);
ssize_t ret = -ENODATA;

mutex_lock(&stp_work_mutex);
if (stpinfo_valid())
ret = sprintf(buf, "%i\n", stp_info.ctn);
mutex_unlock(&stp_work_mutex);
return ret;
}

static DEVICE_ATTR(ctn_type, 0400, stp_ctn_type_show, NULL);
Expand All @@ -719,9 +743,13 @@ static ssize_t stp_dst_offset_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
if (!stp_online || !(stp_info.vbits & 0x2000))
return -ENODATA;
return sprintf(buf, "%i\n", (int)(s16) stp_info.dsto);
ssize_t ret = -ENODATA;

mutex_lock(&stp_work_mutex);
if (stpinfo_valid() && (stp_info.vbits & 0x2000))
ret = sprintf(buf, "%i\n", (int)(s16) stp_info.dsto);
mutex_unlock(&stp_work_mutex);
return ret;
}

static DEVICE_ATTR(dst_offset, 0400, stp_dst_offset_show, NULL);
Expand All @@ -730,9 +758,13 @@ static ssize_t stp_leap_seconds_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
if (!stp_online || !(stp_info.vbits & 0x8000))
return -ENODATA;
return sprintf(buf, "%i\n", (int)(s16) stp_info.leaps);
ssize_t ret = -ENODATA;

mutex_lock(&stp_work_mutex);
if (stpinfo_valid() && (stp_info.vbits & 0x8000))
ret = sprintf(buf, "%i\n", (int)(s16) stp_info.leaps);
mutex_unlock(&stp_work_mutex);
return ret;
}

static DEVICE_ATTR(leap_seconds, 0400, stp_leap_seconds_show, NULL);
Expand All @@ -741,9 +773,13 @@ static ssize_t stp_stratum_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
if (!stp_online)
return -ENODATA;
return sprintf(buf, "%i\n", (int)(s16) stp_info.stratum);
ssize_t ret = -ENODATA;

mutex_lock(&stp_work_mutex);
if (stpinfo_valid())
ret = sprintf(buf, "%i\n", (int)(s16) stp_info.stratum);
mutex_unlock(&stp_work_mutex);
return ret;
}

static DEVICE_ATTR(stratum, 0400, stp_stratum_show, NULL);
Expand All @@ -752,9 +788,13 @@ static ssize_t stp_time_offset_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
if (!stp_online || !(stp_info.vbits & 0x0800))
return -ENODATA;
return sprintf(buf, "%i\n", (int) stp_info.tto);
ssize_t ret = -ENODATA;

mutex_lock(&stp_work_mutex);
if (stpinfo_valid() && (stp_info.vbits & 0x0800))
ret = sprintf(buf, "%i\n", (int) stp_info.tto);
mutex_unlock(&stp_work_mutex);
return ret;
}

static DEVICE_ATTR(time_offset, 0400, stp_time_offset_show, NULL);
Expand All @@ -763,9 +803,13 @@ static ssize_t stp_time_zone_offset_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
if (!stp_online || !(stp_info.vbits & 0x4000))
return -ENODATA;
return sprintf(buf, "%i\n", (int)(s16) stp_info.tzo);
ssize_t ret = -ENODATA;

mutex_lock(&stp_work_mutex);
if (stpinfo_valid() && (stp_info.vbits & 0x4000))
ret = sprintf(buf, "%i\n", (int)(s16) stp_info.tzo);
mutex_unlock(&stp_work_mutex);
return ret;
}

static DEVICE_ATTR(time_zone_offset, 0400,
Expand All @@ -775,9 +819,13 @@ static ssize_t stp_timing_mode_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
if (!stp_online)
return -ENODATA;
return sprintf(buf, "%i\n", stp_info.tmd);
ssize_t ret = -ENODATA;

mutex_lock(&stp_work_mutex);
if (stpinfo_valid())
ret = sprintf(buf, "%i\n", stp_info.tmd);
mutex_unlock(&stp_work_mutex);
return ret;
}

static DEVICE_ATTR(timing_mode, 0400, stp_timing_mode_show, NULL);
Expand All @@ -786,9 +834,13 @@ static ssize_t stp_timing_state_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
if (!stp_online)
return -ENODATA;
return sprintf(buf, "%i\n", stp_info.tst);
ssize_t ret = -ENODATA;

mutex_lock(&stp_work_mutex);
if (stpinfo_valid())
ret = sprintf(buf, "%i\n", stp_info.tst);
mutex_unlock(&stp_work_mutex);
return ret;
}

static DEVICE_ATTR(timing_state, 0400, stp_timing_state_show, NULL);
Expand Down

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