From: Nathan Chancellor <natechancellor@gmail.com> 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/6d485ff455ea2b37fef9e06e426dae6c... 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; -- 2.22.0