5.10-stable review patch. If anyone has any objections, please let me know.
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From: Christian Marangi ansuelsmth@gmail.com
[ Upstream commit ea167a7fc2426f7685c3735e104921c1a20a6d3f ]
Commit 3c0897c180c6 ("cpufreq: Use scnprintf() for avoiding potential buffer overflow") switched from snprintf to the more secure scnprintf but never updated the exit condition for PAGE_SIZE.
As the commit say and as scnprintf document, what scnprintf returns what is actually written not counting the '\0' end char. This results in the case of len exceeding the size, len set to PAGE_SIZE - 1, as it can be written at max PAGE_SIZE - 1 (as '\0' is not counted)
Because of len is never set to PAGE_SIZE, the function never break early, never prints the warning and never return -EFBIG.
Fix this by changing the condition to PAGE_SIZE - 1 to correctly trigger the error.
Cc: 5.10+ stable@vger.kernel.org # 5.10+ Fixes: 3c0897c180c6 ("cpufreq: Use scnprintf() for avoiding potential buffer overflow") Signed-off-by: Christian Marangi ansuelsmth@gmail.com [ rjw: Subject and changelog edits ] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/cpufreq/cpufreq_stats.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c index 6cd5c8ab5d49f..ab856dd2d5fc0 100644 --- a/drivers/cpufreq/cpufreq_stats.c +++ b/drivers/cpufreq/cpufreq_stats.c @@ -131,25 +131,25 @@ static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf) len += scnprintf(buf + len, PAGE_SIZE - len, " From : To\n"); len += scnprintf(buf + len, PAGE_SIZE - len, " : "); for (i = 0; i < stats->state_num; i++) { - if (len >= PAGE_SIZE) + if (len >= PAGE_SIZE - 1) break; len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ", stats->freq_table[i]); } - if (len >= PAGE_SIZE) - return PAGE_SIZE; + if (len >= PAGE_SIZE - 1) + return PAGE_SIZE - 1;
len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
for (i = 0; i < stats->state_num; i++) { - if (len >= PAGE_SIZE) + if (len >= PAGE_SIZE - 1) break;
len += scnprintf(buf + len, PAGE_SIZE - len, "%9u: ", stats->freq_table[i]);
for (j = 0; j < stats->state_num; j++) { - if (len >= PAGE_SIZE) + if (len >= PAGE_SIZE - 1) break;
if (pending) @@ -159,12 +159,12 @@ static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ", count); } - if (len >= PAGE_SIZE) + if (len >= PAGE_SIZE - 1) break; len += scnprintf(buf + len, PAGE_SIZE - len, "\n"); }
- if (len >= PAGE_SIZE) { + if (len >= PAGE_SIZE - 1) { pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n"); return -EFBIG; }