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perf: Fix u16 overflows

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Vince reported that its possible to overflow the various size fields
and get weird stuff if you stick too many events in a group.

Put a lid on this by requiring the fixed record size not exceed 16k.
This is still a fair amount of events (silly amount really) and leaves
plenty room for callchains and stack dwarves while also avoiding
overflowing the u16 variables.

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-09-09 19:06:33 +02:00 committed by Ingo Molnar
parent f55fc2a57c
commit a723968c0e
1 changed files with 40 additions and 10 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

50
kernel/events/core.c
View file

@ -1243,11 +1243,7 @@ static inline void perf_event__state_init(struct perf_event *event)
PERF_EVENT_STATE_INACTIVE;
}
/*
* Called at perf_event creation and when events are attached/detached from a
* group.
*/
static void perf_event__read_size(struct perf_event *event)
static void __perf_event_read_size(struct perf_event *event, int nr_siblings)
{
int entry = sizeof(u64); /* value */
int size = 0;
@ -1263,7 +1259,7 @@ static void perf_event__read_size(struct perf_event *event)
entry += sizeof(u64);
if (event->attr.read_format & PERF_FORMAT_GROUP) {
nr += event->group_leader->nr_siblings;
nr += nr_siblings;
size += sizeof(u64);
}
@ -1271,14 +1267,11 @@ static void perf_event__read_size(struct perf_event *event)
event->read_size = size;
}
static void perf_event__header_size(struct perf_event *event)
static void __perf_event_header_size(struct perf_event *event, u64 sample_type)
{
struct perf_sample_data *data;
u64 sample_type = event->attr.sample_type;
u16 size = 0;
perf_event__read_size(event);
if (sample_type & PERF_SAMPLE_IP)
size += sizeof(data->ip);
@ -1303,6 +1296,17 @@ static void perf_event__header_size(struct perf_event *event)
event->header_size = size;
}
/*
* Called at perf_event creation and when events are attached/detached from a
* group.
*/
static void perf_event__header_size(struct perf_event *event)
{
__perf_event_read_size(event,
event->group_leader->nr_siblings);
__perf_event_header_size(event, event->attr.sample_type);
}
static void perf_event__id_header_size(struct perf_event *event)
{
struct perf_sample_data *data;
@ -1330,6 +1334,27 @@ static void perf_event__id_header_size(struct perf_event *event)
event->id_header_size = size;
}
static bool perf_event_validate_size(struct perf_event *event)
{
/*
* The values computed here will be over-written when we actually
* attach the event.
*/
__perf_event_read_size(event, event->group_leader->nr_siblings + 1);
__perf_event_header_size(event, event->attr.sample_type & ~PERF_SAMPLE_READ);
perf_event__id_header_size(event);
/*
* Sum the lot; should not exceed the 64k limit we have on records.
* Conservative limit to allow for callchains and other variable fields.
*/
if (event->read_size + event->header_size +
event->id_header_size + sizeof(struct perf_event_header) >= 16*1024)
return false;
return true;
}
static void perf_group_attach(struct perf_event *event)
{
struct perf_event *group_leader = event->group_leader, *pos;
@ -8302,6 +8327,11 @@ SYSCALL_DEFINE5(perf_event_open,
mutex_lock(&ctx->mutex);
}
if (!perf_event_validate_size(event)) {
err = -E2BIG;
goto err_locked;
}
/*
* Must be under the same ctx::mutex as perf_install_in_context(),
* because we need to serialize with concurrent event creation.