linux-kernel - [PATCH AUTOSEL 4.14 091/115] printk: Give error on attempt to set log buffer length to over 2G

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Date:   Tue, 12 Nov 2019 20:55:58 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     He Zhe <zhe.he@...driver.com>, rostedt@...dmis.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.14 091/115] printk: Give error on attempt to set log buffer length to over 2G

From: He Zhe <zhe.he@...driver.com>

[ Upstream commit e6fe3e5b7d16e8f146a4ae7fe481bc6e97acde1e ]

The current printk() is ready to handle log buffer size up to 2G.
Give an explicit error for users who want to use larger log buffer.

Also fix printk formatting to show the 2G as a positive number.

Link: http://lkml.kernel.org/r/20181008135916.gg4kkmoki5bgtco5@pathway.suse.cz
Cc: rostedt@...dmis.org
Cc: linux-kernel@...r.kernel.org
Suggested-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Signed-off-by: He Zhe <zhe.he@...driver.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
[pmladek: Fixed to the really safe limit 2GB.]
Signed-off-by: Petr Mladek <pmladek@...e.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/printk/printk.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 5aa96098c64d3..5b33c14ab8b25 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -432,6 +432,7 @@ 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)
 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
 static char *log_buf = __log_buf;
 static u32 log_buf_len = __LOG_BUF_LEN;
@@ -1032,18 +1033,23 @@ void log_buf_vmcoreinfo_setup(void)
 static unsigned long __initdata new_log_buf_len;
 
 /* we practice scaling the ring buffer by powers of 2 */
-static void __init log_buf_len_update(unsigned size)
+static void __init log_buf_len_update(u64 size)
 {
+	if (size > (u64)LOG_BUF_LEN_MAX) {
+		size = (u64)LOG_BUF_LEN_MAX;
+		pr_err("log_buf over 2G is not supported.\n");
+	}
+
 	if (size)
 		size = roundup_pow_of_two(size);
 	if (size > log_buf_len)
-		new_log_buf_len = size;
+		new_log_buf_len = (unsigned long)size;
 }
 
 /* save requested log_buf_len since it's too early to process it */
 static int __init log_buf_len_setup(char *str)
 {
-	unsigned int size;
+	u64 size;
 
 	if (!str)
 		return -EINVAL;
@@ -1113,7 +1119,7 @@ void __init setup_log_buf(int early)
 	}
 
 	if (unlikely(!new_log_buf)) {
-		pr_err("log_buf_len: %ld bytes not available\n",
+		pr_err("log_buf_len: %lu bytes not available\n",
 			new_log_buf_len);
 		return;
 	}
@@ -1126,8 +1132,8 @@ void __init setup_log_buf(int early)
 	memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
 	logbuf_unlock_irqrestore(flags);
 
-	pr_info("log_buf_len: %d bytes\n", log_buf_len);
-	pr_info("early log buf free: %d(%d%%)\n",
+	pr_info("log_buf_len: %u bytes\n", log_buf_len);
+	pr_info("early log buf free: %u(%u%%)\n",
 		free, (free * 100) / __LOG_BUF_LEN);
 }
 
-- 
2.20.1