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From: Dan Carpenter <dan.carpenter@oracle.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: [PATCH] tracing: Fix an off by one in __next()
Date: Wed, 20 Jun 2018 14:08:00 +0300
Message-ID: <20180620110758.crunhd5bfep7zuiz@kili.mountain> (raw)

The > should be >= to prevent an off by one bug.

From reviewing the code, it seems possible for
stack_trace_max.nr_entries to be set to .max_entries and in that case we
would be reading one element beyond the end of the stack_dump_trace[]
array.  If it's not set to .max_entries then the bug doesn't affect
runtime.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 4237eba4ef20..6e3edd745c68 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -286,7 +286,7 @@ __next(struct seq_file *m, loff_t *pos)
 {
 	long n = *pos - 1;
 
-	if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
+	if (n >= stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
 		return NULL;
 
 	m->private = (void *)n;

             reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-20 11:08 Dan Carpenter [this message]
2018-11-27 18:44 ` Steven Rostedt
2018-11-27 20:04   ` Dan Carpenter

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