linux-kernel - [PATCH 2/9] tracing: Dont use p->len field to determine output in __print

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Date:	Wed, 22 Feb 2012 09:40:38 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Andrew Vagin <avagin@...nvz.org>
Subject: [PATCH 2/9] tracing: Dont use p->len field to determine output in __print_*()
 functions

From: Steven Rostedt <srostedt@...hat.com>

If more than one __print_*() function is used in a tracepoint
(__print_flags(), __print_symbols(), etc), then the temp seq buffer will
not be zero on entry. Using the temp seq buffer's length to know if
data has been printed or not in the current function is incorrect and
may produce incorrect results.

Currently, no in-tree tracepoint causes this bug, but new ones may
be created.

Cc: Andrew Vagin <avagin@...nvz.org>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/trace/trace_output.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 3efd718..c5a0187 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -319,7 +319,7 @@ ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
 
 	/* check for left over flags */
 	if (flags) {
-		if (p->len && delim)
+		if (!first && delim)
 			trace_seq_puts(p, delim);
 		trace_seq_printf(p, "0x%lx", flags);
 	}
@@ -346,7 +346,7 @@ ftrace_print_symbols_seq(struct trace_seq *p, unsigned long val,
 		break;
 	}
 
-	if (!p->len)
+	if (ret == (const char *)(p->buffer + p->len))
 		trace_seq_printf(p, "0x%lx", val);
 		
 	trace_seq_putc(p, 0);
@@ -372,7 +372,7 @@ ftrace_print_symbols_seq_u64(struct trace_seq *p, unsigned long long val,
 		break;
 	}
 
-	if (!p->len)
+	if (ret == (const char *)(p->buffer + p->len))
 		trace_seq_printf(p, "0x%llx", val);
 
 	trace_seq_putc(p, 0);
-- 
1.7.8.3



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