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authorLinus Torvalds <torvalds@linux-foundation.org>2016-04-28 20:19:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-04-28 20:19:04 -0700
commit814dd9481d2045cc99a10a45d267a6167c5cd8ff (patch)
tree1f3218b72700fe097f67e5d29b79ac4a351d9006 /kernel
parent2113caed87dd372e5ca2d9b3cba415f4da38936b (diff)
parentcf3beb7c90a8efa16a06b26634cddddc92bb819c (diff)
Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar: "x86 PMU driver fixes plus a core code race fix" * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: perf/x86/intel: Fix incorrect lbr_sel_mask value perf/x86/intel/pt: Don't die on VMXON perf/core: Fix perf_event_open() vs. execve() race perf/x86/amd: Set the size of event map array to PERF_COUNT_HW_MAX perf/core: Make sysctl_perf_cpu_time_max_percent conform to documentation perf/x86/intel/rapl: Add missing Haswell model perf/x86/intel: Add model number for Skylake Server to perf
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c55
1 files changed, 38 insertions, 17 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 52bedc5a5aaa..4e2ebf6f2f1f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -412,7 +412,8 @@ int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
if (ret || !write)
return ret;
- if (sysctl_perf_cpu_time_max_percent == 100) {
+ if (sysctl_perf_cpu_time_max_percent == 100 ||
+ sysctl_perf_cpu_time_max_percent == 0) {
printk(KERN_WARNING
"perf: Dynamic interrupt throttling disabled, can hang your system!\n");
WRITE_ONCE(perf_sample_allowed_ns, 0);
@@ -1105,6 +1106,7 @@ static void put_ctx(struct perf_event_context *ctx)
* function.
*
* Lock order:
+ * cred_guard_mutex
* task_struct::perf_event_mutex
* perf_event_context::mutex
* perf_event::child_mutex;
@@ -3420,7 +3422,6 @@ static struct task_struct *
find_lively_task_by_vpid(pid_t vpid)
{
struct task_struct *task;
- int err;
rcu_read_lock();
if (!vpid)
@@ -3434,16 +3435,7 @@ find_lively_task_by_vpid(pid_t vpid)
if (!task)
return ERR_PTR(-ESRCH);
- /* Reuse ptrace permission checks for now. */
- err = -EACCES;
- if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
- goto errout;
-
return task;
-errout:
- put_task_struct(task);
- return ERR_PTR(err);
-
}
/*
@@ -8413,6 +8405,24 @@ SYSCALL_DEFINE5(perf_event_open,
get_online_cpus();
+ if (task) {
+ err = mutex_lock_interruptible(&task->signal->cred_guard_mutex);
+ if (err)
+ goto err_cpus;
+
+ /*
+ * Reuse ptrace permission checks for now.
+ *
+ * We must hold cred_guard_mutex across this and any potential
+ * perf_install_in_context() call for this new event to
+ * serialize against exec() altering our credentials (and the
+ * perf_event_exit_task() that could imply).
+ */
+ err = -EACCES;
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
+ goto err_cred;
+ }
+
if (flags & PERF_FLAG_PID_CGROUP)
cgroup_fd = pid;
@@ -8420,7 +8430,7 @@ SYSCALL_DEFINE5(perf_event_open,
NULL, NULL, cgroup_fd);
if (IS_ERR(event)) {
err = PTR_ERR(event);
- goto err_cpus;
+ goto err_cred;
}
if (is_sampling_event(event)) {
@@ -8479,11 +8489,6 @@ SYSCALL_DEFINE5(perf_event_open,
goto err_context;
}
- if (task) {
- put_task_struct(task);
- task = NULL;
- }
-
/*
* Look up the group leader (we will attach this event to it):
*/
@@ -8581,6 +8586,11 @@ SYSCALL_DEFINE5(perf_event_open,
WARN_ON_ONCE(ctx->parent_ctx);
+ /*
+ * This is the point on no return; we cannot fail hereafter. This is
+ * where we start modifying current state.
+ */
+
if (move_group) {
/*
* See perf_event_ctx_lock() for comments on the details
@@ -8652,6 +8662,11 @@ SYSCALL_DEFINE5(perf_event_open,
mutex_unlock(&gctx->mutex);
mutex_unlock(&ctx->mutex);
+ if (task) {
+ mutex_unlock(&task->signal->cred_guard_mutex);
+ put_task_struct(task);
+ }
+
put_online_cpus();
mutex_lock(&current->perf_event_mutex);
@@ -8684,6 +8699,9 @@ err_alloc:
*/
if (!event_file)
free_event(event);
+err_cred:
+ if (task)
+ mutex_unlock(&task->signal->cred_guard_mutex);
err_cpus:
put_online_cpus();
err_task:
@@ -8968,6 +8986,9 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
/*
* When a child task exits, feed back event values to parent events.
+ *
+ * Can be called with cred_guard_mutex held when called from
+ * install_exec_creds().
*/
void perf_event_exit_task(struct task_struct *child)
{