From f6675872db57305fa957021efc788f9983ed3b67 Mon Sep 17 00:00:00 2001 From: Andreas Ziegler Date: Wed, 6 Feb 2019 20:00:13 +0100 Subject: [PATCH] tracing: probeevent: Correctly update remaining space in dynamic area Commit 9178412ddf5a ("tracing: probeevent: Return consumed bytes of dynamic area") improved the string fetching mechanism by returning the number of required bytes after copying the argument to the dynamic area. However, this return value is now only used to increment the pointer inside the dynamic area but misses updating the 'maxlen' variable which indicates the remaining space in the dynamic area. This means that fetch_store_string() always reads the *total* size of the dynamic area from the data_loc pointer instead of the *remaining* size (and passes it along to strncpy_from_{user,unsafe}) even if we're already about to copy data into the middle of the dynamic area. Link: http://lkml.kernel.org/r/20190206190013.16405-1-andreas.ziegler@fau.de Cc: Ingo Molnar Cc: stable@vger.kernel.org Fixes: 9178412ddf5a ("tracing: probeevent: Return consumed bytes of dynamic area") Acked-by: Masami Hiramatsu Signed-off-by: Andreas Ziegler Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_probe_tmpl.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h index 5c56afc17cf8..4737bb8c07a3 100644 --- a/kernel/trace/trace_probe_tmpl.h +++ b/kernel/trace/trace_probe_tmpl.h @@ -180,10 +180,12 @@ store_trace_args(void *data, struct trace_probe *tp, struct pt_regs *regs, if (unlikely(arg->dynamic)) *dl = make_data_loc(maxlen, dyndata - base); ret = process_fetch_insn(arg->code, regs, dl, base); - if (unlikely(ret < 0 && arg->dynamic)) + if (unlikely(ret < 0 && arg->dynamic)) { *dl = make_data_loc(0, dyndata - base); - else + } else { dyndata += ret; + maxlen -= ret; + } } } -- 2.30.2