From: Kuan-Wei Chiu visitorckw@gmail.com
[ 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 visitorckw@gmail.com Acked-by: Petr Mladek pmladek@suse.com Link: https://lore.kernel.org/r/20240928113608.1438087-1-visitorckw@gmail.com Signed-off-by: Petr Mladek pmladek@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/printk/printk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ae1a97dd0c3cb..f6e1e154d9c18 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -457,7 +457,7 @@ static u32 clear_idx; /* record buffer */ #define LOG_ALIGN __alignof__(struct printk_log) #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;