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Message-ID: <20110501034141.GA13473@chii>
Date: Sun, 1 May 2011 11:41:41 +0800
From: Xiaochen Wang <wangxiaochen0@...il.com>
To: Jean Sacren <sakiwit@...il.com>, Michal Marek <mmarek@...e.cz>,
linux-kernel@...r.kernel.org
Subject: [PATCH] scripts/kallsyms.c: fix potential segfault
Description:
This bug hardly appears during real kernel compiling,
because the vmlinux symbols table is huge.
But we can still catch it under strict condition , as follows.
$ echo "c101b97b T do_fork" | ./scripts/kallsyms --all-symbols
#include <asm/types.h>
......
......
.globl kallsyms_token_table
ALGN
kallsyms_token_table:
Segmentation fault (core dumped)
$
If symbols table is small, all entries in token_profit[0x10000] may
decrease to 0 after several calls of compress_symbols() in optimize_result().
In that case, find_best_token() always return 0 and
best_table[i] is set to "\0\0" and best_table_len[i] is set to 2.
As a result, expand_symbol(best_table[0]="\0\0", best_table_len[0]=2, buf)
in write_src() will run in infinite recursion until stack overflows,
causing segfault.
This patch checks the find_best_token() return value. If all entries in
token_profit[0x10000] become 0 according to return value, it breaks the loop
in optimize_result().
And expand_symbol() works well when best_table_len[i] is 0.
Signed-off-by: Xiaochen Wang <wangxiaochen0@...il.com>
---
scripts/kallsyms.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 60dd3eb..487ac6f 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -500,6 +500,8 @@ static void optimize_result(void)
/* find the token with the breates profit value */
best = find_best_token();
+ if (token_profit[best] == 0)
+ break;
/* place it in the "best" table */
best_table_len[i] = 2;
--
1.7.2.3
--
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