[tip:perfcounters/core] perf_counter: Fix perf_output_copy() WARN to account for overflow

tip-bot for Peter Zijlstra
2009-05-15T08:46:30Z

Commit-ID: 53020fe81eecd0b7be295868ce5850ef8f41074e
Gitweb: http://git.kernel.org/tip/53020fe81eecd0b7be295868ce5850ef8f41074e
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Wed, 13 May 2009 21:26:19 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 15 May 2009 09:46:59 +0200

perf_counter: Fix perf_output_copy() WARN to account for overflow

The simple reservation test in perf_output_copy() failed to take
unsigned int overflow into account, fix this.

[ Impact: fix false positive warning with more than 4GB of profiling data ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
kernel/perf_counter.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index ff166c1..985be0b 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1927,7 +1927,11 @@ static void perf_output_copy(struct perf_output_handle *handle,

handle->offset = offset;

- WARN_ON_ONCE(handle->offset > handle->head);
+ /*
+ * Check we didn't copy past our reservation window, taking the
+ * possible unsigned int wrap into account.
+ */
+ WARN_ON_ONCE(((int)(handle->head - handle->offset)) < 0);
}

#define perf_output_put(handle, x) \