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authorSergey Senozhatsky <sergey.senozhatsky@gmail.com>2018-10-10 20:33:08 +0900
committerPetr Mladek <pmladek@suse.com>2018-10-12 10:44:17 +0200
commitd2130e82e9454304e9b91ba9da551b5989af8c27 (patch)
treefb05902bc7c19b4d37b8ae59e78e794ddfcd8afd /kernel/printk
parent0e96a19c4450253c3ddcff69140b1096f2c2adaf (diff)
printk: fix integer overflow in setup_log_buf()
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>
Diffstat (limited to 'kernel/printk')
-rw-r--r--kernel/printk/printk.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 505663bb4f1f..b77150ad1965 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1098,7 +1098,7 @@ 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;