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PM / devfreq: Fix buffer overflow in trans_stat_show

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commit 08e23d05fa6dc4fc13da0ccf09defdd4bbc92ff4 upstream.

Fix buffer overflow in trans_stat_show().

Convert simple snprintf to the more secure scnprintf with size of
PAGE_SIZE.

Add condition checking if we are exceeding PAGE_SIZE and exit early from
loop. Also add at the end a warning that we exceeded PAGE_SIZE and that
stats is disabled.

Return -EFBIG in the case where we don't have enough space to write the
full transition table.

Also document in the ABI that this function can return -EFBIG error.

Link: https://lore.kernel.org/all/20231024183016.14648-2-ansuelsmth@gmail.com/
Cc: stable@vger.kernel.org
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218041
Fixes: e552bbaf5b98 ("PM / devfreq: Add sysfs node for representing frequency transition information.")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christian Marangi 2023-10-24 20:30:15 +02:00 committed by Greg Kroah-Hartman
parent f4518de40a
commit 8a7729cda2
2 changed files with 43 additions and 19 deletions
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3
Documentation/ABI/testing/sysfs-class-devfreq
View File

@ -52,6 +52,9 @@ Description:
echo 0 > /sys/class/devfreq/.../trans_stat echo 0 > /sys/class/devfreq/.../trans_stat
If the transition table is bigger than PAGE_SIZE, reading
this will return an -EFBIG error.
What: /sys/class/devfreq/.../available_frequencies What: /sys/class/devfreq/.../available_frequencies
Date: October 2012 Date: October 2012
Contact: Nishanth Menon <nm@ti.com> Contact: Nishanth Menon <nm@ti.com>

51
drivers/devfreq/devfreq.c
View File

@ -1687,7 +1687,7 @@ static ssize_t trans_stat_show(struct device *dev,
struct device_attribute *attr, char *buf) struct device_attribute *attr, char *buf)
{ {
struct devfreq *df = to_devfreq(dev); struct devfreq *df = to_devfreq(dev);
ssize_t len; ssize_t len = 0;
int i, j; int i, j;
unsigned int max_state; unsigned int max_state;
@ -1696,7 +1696,7 @@ static ssize_t trans_stat_show(struct device *dev,
max_state = df->max_state; max_state = df->max_state;
if (max_state == 0) if (max_state == 0)
return sprintf(buf, "Not Supported.\n"); return scnprintf(buf, PAGE_SIZE, "Not Supported.\n");
mutex_lock(&df->lock); mutex_lock(&df->lock);
if (!df->stop_polling && if (!df->stop_polling &&
@ -1706,31 +1706,52 @@ static ssize_t trans_stat_show(struct device *dev,
} }
mutex_unlock(&df->lock); mutex_unlock(&df->lock);
len = sprintf(buf, " From : To\n"); len += scnprintf(buf + len, PAGE_SIZE - len, " From : To\n");
len += sprintf(buf + len, " :"); len += scnprintf(buf + len, PAGE_SIZE - len, " :");
for (i = 0; i < max_state; i++) for (i = 0; i < max_state; i++) {
len += sprintf(buf + len, "%10lu", if (len >= PAGE_SIZE - 1)
break;
len += scnprintf(buf + len, PAGE_SIZE - len, "%10lu",
df->freq_table[i]); df->freq_table[i]);
}
if (len >= PAGE_SIZE - 1)
return PAGE_SIZE - 1;
len += sprintf(buf + len, " time(ms)\n"); len += scnprintf(buf + len, PAGE_SIZE - len, " time(ms)\n");
for (i = 0; i < max_state; i++) { for (i = 0; i < max_state; i++) {
if (len >= PAGE_SIZE - 1)
break;
if (df->freq_table[i] == df->previous_freq) if (df->freq_table[i] == df->previous_freq)
len += sprintf(buf + len, "*"); len += scnprintf(buf + len, PAGE_SIZE - len, "*");
else else
len += sprintf(buf + len, " "); len += scnprintf(buf + len, PAGE_SIZE - len, " ");
if (len >= PAGE_SIZE - 1)
break;
len += sprintf(buf + len, "%10lu:", df->freq_table[i]); len += scnprintf(buf + len, PAGE_SIZE - len, "%10lu:",
for (j = 0; j < max_state; j++) df->freq_table[i]);
len += sprintf(buf + len, "%10u", for (j = 0; j < max_state; j++) {
if (len >= PAGE_SIZE - 1)
break;
len += scnprintf(buf + len, PAGE_SIZE - len, "%10u",
df->stats.trans_table[(i * max_state) + j]); df->stats.trans_table[(i * max_state) + j]);
}
len += sprintf(buf + len, "%10llu\n", (u64) if (len >= PAGE_SIZE - 1)
break;
len += scnprintf(buf + len, PAGE_SIZE - len, "%10llu\n", (u64)
jiffies64_to_msecs(df->stats.time_in_state[i])); jiffies64_to_msecs(df->stats.time_in_state[i]));
} }
len += sprintf(buf + len, "Total transition : %u\n", if (len < PAGE_SIZE - 1)
len += scnprintf(buf + len, PAGE_SIZE - len, "Total transition : %u\n",
df->stats.total_trans); df->stats.total_trans);
if (len >= PAGE_SIZE - 1) {
pr_warn_once("devfreq transition table exceeds PAGE_SIZE. Disabling\n");
return -EFBIG;
}
return len; return len;
} }