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printk: Convert a use of sprintf to snprintf in console_unlock

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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: 6d485ff455
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>
This commit is contained in:
Nathan Chancellor 2020-01-30 15:16:44 -07:00 committed by Petr Mladek
parent a4fe2b4d87
commit 5661dd95a2
1 changed files with 3 additions and 3 deletions
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6
kernel/printk/printk.c
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@ -2413,9 +2413,9 @@ again:
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;