From: Kuan-Wei Chiu Date: Sat, 28 Sep 2024 11:36:08 +0000 (+0800) Subject: printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX X-Git-Tag: v5.10.235~332 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=dfb7b179741ee09506dc7719d92f9e1cea01f10e;p=thirdparty%2Fkernel%2Fstable.git printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX [ Upstream commit 3d6f83df8ff2d5de84b50377e4f0d45e25311c7a ] Shifting 1 << 31 on a 32-bit int causes signed integer overflow, which leads to undefined behavior. To prevent this, cast 1 to u32 before performing the shift, ensuring well-defined behavior. This change explicitly avoids any potential overflow by ensuring that the shift occurs on an unsigned 32-bit integer. Signed-off-by: Kuan-Wei Chiu Acked-by: Petr Mladek Link: https://lore.kernel.org/r/20240928113608.1438087-1-visitorckw@gmail.com Signed-off-by: Petr Mladek Signed-off-by: Sasha Levin --- diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index a8af93cbc2936..3a7fd61c0e7be 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -420,7 +420,7 @@ static u64 clear_seq; /* record buffer */ #define LOG_ALIGN __alignof__(unsigned long) #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) -#define LOG_BUF_LEN_MAX (u32)(1 << 31) +#define LOG_BUF_LEN_MAX ((u32)1 << 31) static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN); static char *log_buf = __log_buf; static u32 log_buf_len = __LOG_BUF_LEN;