From: Gil Fruchter Currently exception occures due to access beyond buffer_iter range while using index of cpu bigger than num_possible_cpus(). Below there is an example for such exception when we use cpus 0,1,16,17. In order to fix buffer allocation size for non-continuous cpu ids we allocate according to the max cpu id and not according to the amount of possible cpus. Example: $ cat /sys/kernel/debug/tracing/per_cpu/cpu1/trace Path: /bin/busybox CPU: 0 PID: 82 Comm: cat Not tainted 4.0.0 #29 task: 80734c80 ti: 80012000 task.ti: 80012000 [ECR ]: 0x00220100 => Invalid Read @ 0x00000000 by insn @ 0x800abafc [EFA ]: 0x00000000 [BLINK ]: ring_buffer_read_finish+0x24/0x64 [ERET ]: rb_check_pages+0x20/0x188 [STAT32]: 0x00001a00 : BTA: 0x800abafc SP: 0x80013f0c FP: 0x57719cf8 LPS: 0x200036b4 LPE: 0x200036b8 LPC: 0x00000000 r00: 0x8002aca0 r01: 0x00001606 r02: 0x00000000 r03: 0x00000001 r04: 0x00000000 r05: 0x804b4954 r06: 0x00030003 r07: 0x8002a260 r08: 0x00000286 r09: 0x00080002 r10: 0x00001006 r11: 0x807351a4 r12: 0x00000001 Stack Trace: rb_check_pages+0x20/0x188 ring_buffer_read_finish+0x24/0x64 tracing_release+0x4e/0x170 __fput+0x62/0x158 task_work_run+0xa2/0xd4 do_notify_resume+0x52/0x7c resume_user_mode_begin+0xdc/0xe0 Link: http://lkml.kernel.org/r/1433835155-6894-3-git-send-email-gilf@ezchip.com Signed-off-by: Noam Camus Signed-off-by: Gil Fruchter Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5d219384b4d1..59814adc39d6 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3035,7 +3035,7 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot) if (!iter) return ERR_PTR(-ENOMEM); - iter->buffer_iter = kcalloc(num_possible_cpus(), sizeof(*iter->buffer_iter), + iter->buffer_iter = kcalloc(nr_cpu_ids, sizeof(*iter->buffer_iter), GFP_KERNEL); if (!iter->buffer_iter) goto release; -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/