[tip:perf/urgent] perf session: Fix infinite loop in __perf_session__process_events

tip-bot for Arnaldo Carvalho de Melo
2011-01-11T11:12:45Z

Commit-ID: 3d03e2ea74103a50c23d6ab1906cf73399c0dafb
Gitweb: http://git.kernel.org/tip/3d03e2ea74103a50c23d6ab1906cf73399c0dafb
Author: Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Mon, 10 Jan 2011 21:37:57 -0200
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 10 Jan 2011 22:23:08 -0200

perf session: Fix infinite loop in __perf_session__process_events

In this if statement:

if (head + event->header.size >= mmap_size) {
if (mmaps[map_idx]) {
munmap(mmaps[map_idx], mmap_size);
mmaps[map_idx] = NULL;
}

page_offset = page_size * (head / page_size);
file_offset += page_offset;
head -= page_offset;
goto remap;
}

With, for instance, these values:

head=2992
event->header.size=48
mmap_size=3040

We end up endlessly looping back to remap. Off by one.

Problem introduced in 55b4462.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Ingo Molnar <mingo@elte.hu>
Reported-by: David Ahern <daahern@cisco.com>
Bisected-by: David Ahern <daahern@cisco.com>
Tested-by: David Ahern <daahern@cisco.com>
Cc: David Ahern <daahern@cisco.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/session.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 6fb4694..313dac2 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1007,7 +1007,7 @@ more:
if (size == 0)
size = 8;

- if (head + event->header.size >= mmap_size) {
+ if (head + event->header.size > mmap_size) {
if (mmaps[map_idx]) {
munmap(mmaps[map_idx], mmap_size);
mmaps[map_idx] = NULL;