From ab2bff9a8f87be3710edef3f2f17dee78962a6a1 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Fri, 13 May 2016 09:34:12 -0400 Subject: UPSTREAM: ring-buffer: Prevent overflow of size in ring_buffer_resize() (Cherry picked from commit 59643d1535eb220668692a5359de22545af579f6) If the size passed to ring_buffer_resize() is greater than MAX_LONG - BUF_PAGE_SIZE then the DIV_ROUND_UP() will return zero. Here's the details: # echo 18014398509481980 > /sys/kernel/debug/tracing/buffer_size_kb tracing_entries_write() processes this and converts kb to bytes. 18014398509481980 << 10 = 18446744073709547520 and this is passed to ring_buffer_resize() as unsigned long size. size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); Where DIV_ROUND_UP(a, b) is (a + b - 1)/b BUF_PAGE_SIZE is 4080 and here 18446744073709547520 + 4080 - 1 = 18446744073709551599 where 18446744073709551599 is still smaller than 2^64 2^64 - 18446744073709551599 = 17 But now 18446744073709551599 / 4080 = 4521260802379792 and size = size * 4080 = 18446744073709551360 This is checked to make sure its still greater than 2 * 4080, which it is. Then we convert to the number of buffer pages needed. nr_page = DIV_ROUND_UP(size, BUF_PAGE_SIZE) but this time size is 18446744073709551360 and 2^64 - (18446744073709551360 + 4080 - 1) = -3823 Thus it overflows and the resulting number is less than 4080, which makes 3823 / 4080 = 0 an nr_pages is set to this. As we already checked against the minimum that nr_pages may be, this causes the logic to fail as well, and we crash the kernel. There's no reason to have the two DIV_ROUND_UP() (that's just result of historical code changes), clean up the code and fix this bug. Cc: stable@vger.kernel.org # 3.5+ Fixes: 83f40318dab00 ("ring-buffer: Make removal of ring buffer pages atomic") Signed-off-by: Steven Rostedt Signed-off-by: Willy Tarreau Change-Id: I1147672317a3ad0fc995b1f32baaa050a7976ac4 Bug: 32659848 --- kernel/trace/ring_buffer.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'kernel') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 9c6045a27ba3..7fa26a57a847 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1665,14 +1665,13 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, !cpumask_test_cpu(cpu_id, buffer->cpumask)) return size; - size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); - size *= BUF_PAGE_SIZE; + nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); /* we need a minimum of two pages */ - if (size < BUF_PAGE_SIZE * 2) - size = BUF_PAGE_SIZE * 2; + if (nr_pages < 2) + nr_pages = 2; - nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); + size = nr_pages * BUF_PAGE_SIZE; /* * Don't succeed if resizing is disabled, as a reader might be -- cgit v1.2.3 From 6dc8c51a76e57ae01fa087bdb5450423ce76a373 Mon Sep 17 00:00:00 2001 From: Viresh Kumar Date: Tue, 15 Nov 2016 11:58:52 +0530 Subject: cpufreq: sched: Fix kernel crash on accessing sysfs file If the cpufreq driver hasn't set the CPUFREQ_HAVE_GOVERNOR_PER_POLICY flag, then the kernel will crash on accessing sysfs files for the sched governor. CPUFreq governors we can have the governor specific sysfs files in two places: A. /sys/devices/system/cpu/cpuX/cpufreq/ B. /sys/devices/system/cpu/cpufreq/ The case A. is for governor per policy case, where we can control the governor tunables for each policy separately. The case B. is for system wide tunable values. The schedfreq governor only implements the case A. and not B. The sysfs files in case B will still be present in /sys/devices/system/cpu/cpufreq/, but accessing them will crash kernel as the governor doesn't support that. Moreover the sched governor is pretty new and will be used only for the ARM platforms and there is no need to support the case B at all. Hence use policy->kobj instead of get_governor_parent_kobj(), so that we always create the sysfs files in path A. Signed-off-by: Viresh Kumar --- kernel/sched/cpufreq_sched.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/sched/cpufreq_sched.c b/kernel/sched/cpufreq_sched.c index f6f9b9b3a4a8..d751bc2d0d6e 100644 --- a/kernel/sched/cpufreq_sched.c +++ b/kernel/sched/cpufreq_sched.c @@ -289,7 +289,7 @@ static int cpufreq_sched_policy_init(struct cpufreq_policy *policy) pr_debug("%s: throttle threshold = %u [ns]\n", __func__, gd->up_throttle_nsec); - rc = sysfs_create_group(get_governor_parent_kobj(policy), get_sysfs_attr()); + rc = sysfs_create_group(&policy->kobj, get_sysfs_attr()); if (rc) { pr_err("%s: couldn't create sysfs attributes: %d\n", __func__, rc); goto err; @@ -332,7 +332,7 @@ static int cpufreq_sched_policy_exit(struct cpufreq_policy *policy) put_task_struct(gd->task); } - sysfs_remove_group(get_governor_parent_kobj(policy), get_sysfs_attr()); + sysfs_remove_group(&policy->kobj, get_sysfs_attr()); policy->governor_data = NULL; -- cgit v1.2.3