From df45decfa77ac71641a2324bb08196d164f1e8ee Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <natechancellor@gmail.com>
Date: Mon, 11 Apr 2022 10:35:37 +0800
Subject: [PATCH] printk: Convert a use of sprintf to snprintf in
console_unlock
mainline inclusion
from mainline-v5.8-rc1
commit 5661dd95a2958634485bb1a53f90a6ab621d4b0c
category: bugfix
bugzilla: 91291
CVE: N/A
--------------------------------
When CONFIG_PRINTK is disabled (e.g. when building allnoconfig), clang
warns:
../kernel/printk/printk.c:2416:10: warning: 'sprintf' will always
overflow; destination buffer has size 0, but format string expands to at
least 33 [-Wfortify-source]
len = sprintf(text,
^
1 warning generated.
It is not wrong; text has a zero size when CONFIG_PRINTK is disabled
because LOG_LINE_MAX and PREFIX_MAX are both zero. Change to snprintf so
that this case is explicitly handled without any risk of overflow.
Link: https://github.com/ClangBuiltLinux/linux/issues/846
Link: https://github.com/llvm/llvm-project/commit/6d485ff455ea2b37fef9e06e426dae6c1241b231
Link: http://lkml.kernel.org/r/20200130221644.2273-1-natechancellor@gmail.com
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org
Cc: clang-built-linux@googlegroups.com
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Yi Yang <yiyang13@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
---
kernel/printk/printk.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 0fe45941b5c7..c645a7221d0b 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2423,9 +2423,9 @@ void console_unlock(void)
printk_safe_enter_irqsave(flags);
raw_spin_lock(&logbuf_lock);
if (console_seq < log_first_seq) {
- len = sprintf(text,
- "** %llu printk messages dropped **\n",
- log_first_seq - console_seq);
+ len = snprintf(text, sizeof(text),
+ "** %llu printk messages dropped **\n",
+ log_first_seq - console_seq);
/* messages are gone, move to first one */
console_seq = log_first_seq;
--
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