From: Sergey Senozhatsky sergey.senozhatsky@gmail.com
[ Upstream commit d2130e82e9454304e9b91ba9da551b5989af8c27 ]
The way we calculate logbuf free space percentage overflows signed integer:
int free;
free = __LOG_BUF_LEN - log_next_idx; pr_info("early log buf free: %u(%u%%)\n", free, (free * 100) / __LOG_BUF_LEN);
We support LOG_BUF_LEN of up to 1<<25 bytes. Since setup_log_buf() is called during early init, logbuf is mostly empty, so
__LOG_BUF_LEN - log_next_idx
is close to 1<<25. Thus when we multiply it by 100, we overflow signed integer value range: 100 is 2^6 + 2^5 + 2^2.
Example, booting with LOG_BUF_LEN 1<<25 and log_buf_len=2G boot param:
[ 0.075317] log_buf_len: -2147483648 bytes [ 0.075319] early log buf free: 33549896(-28%)
Make "free" unsigned integer and use appropriate printk() specifier.
Link: http://lkml.kernel.org/r/20181010113308.9337-1-sergey.senozhatsky@gmail.com To: Steven Rostedt rostedt@goodmis.org Cc: linux-kernel@vger.kernel.org Cc: Sergey Senozhatsky sergey.senozhatsky.work@gmail.com Signed-off-by: Sergey Senozhatsky sergey.senozhatsky@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 6607d77afe55a..63528399dc25d 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1044,7 +1044,7 @@ void __init setup_log_buf(int early) { unsigned long flags; char *new_log_buf; - int free; + unsigned int free;
if (log_buf != __log_buf) return;