[PATCH 1/2] hw_breakpoint: Fix cpu check in task_bp_pinned(cpu)

From: Oleg Nesterov
Date: Sat Jun 01 2013 - 14:25:48 EST

trinity fuzzer triggered WARN_ONCE("Can't find any breakpoint slot")
in arch_install_hw_breakpoint() but the problem is not arch-specific.

The problem is, task_bp_pinned(cpu) checks "cpu == iter->cpu" but
this doesn't account the "all cpus" events with iter->cpu < 0.

This means that, say, register_user_hw_breakpoint(tsk) can happily
create the arbitrary number > HBP_NUM of breakpoints which can not
be activated. toggle_bp_task_slot() is equally wrong by the same
reason and nr_task_bp_pinned[] can have negative entries.

Simple test:

# perl -e 'sleep 1 while 1' &
# perf record -e mem:0x10,mem:0x10,mem:0x10,mem:0x10,mem:0x10 -p `pidof perl`

Before this patch this triggers the same problem/WARN_ON(), after
the patch it correctly fails with -ENOSPC.

Reported-by: Vince Weaver <vincent.weaver@xxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
kernel/events/hw_breakpoint.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index ed1c897..29d3abe 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -120,7 +120,7 @@ static int task_bp_pinned(int cpu, struct perf_event *bp, enum bp_type_idx type)
list_for_each_entry(iter, &bp_task_head, hw.bp_list) {
if (iter->hw.bp_target == tsk &&
find_slot_idx(iter) == type &&
- cpu == iter->cpu)
+ (iter->cpu < 0 || cpu == iter->cpu))
count += hw_breakpoint_weight(iter);


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