[PATCH v4 1/4] printk: Fix panic caused by passing log_buf_len to command line

[PATCH v4 1/4] printk: Fix panic caused by passing log_buf_len to command line

[zhe.he]

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

log_buf_len_setup does not check input argument before passing it to
simple_strtoull. The argument would be a NULL pointer if "log_buf_len",
without its value, is set in command line and thus causes the following
panic.

PANIC: early exception 0xe3 IP 10:ffffffffaaeacd0d error 0 cr2 0x0
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.0-rc4-yocto-standard+ #1
[    0.000000] RIP: 0010:_parse_integer_fixup_radix+0xd/0x70
...
[    0.000000] Call Trace:
[    0.000000]  simple_strtoull+0x29/0x70
[    0.000000]  memparse+0x26/0x90
[    0.000000]  log_buf_len_setup+0x17/0x22
[    0.000000]  do_early_param+0x57/0x8e
[    0.000000]  parse_args+0x208/0x320
[    0.000000]  ? rdinit_setup+0x30/0x30
[    0.000000]  parse_early_options+0x29/0x2d
[    0.000000]  ? rdinit_setup+0x30/0x30
[    0.000000]  parse_early_param+0x36/0x4d
[    0.000000]  setup_arch+0x336/0x99e
[    0.000000]  start_kernel+0x6f/0x4ee
[    0.000000]  x86_64_start_reservations+0x24/0x26
[    0.000000]  x86_64_start_kernel+0x6f/0x72
[    0.000000]  secondary_startup_64+0xa4/0xb0

This patch adds a check to prevent the panic.

Signed-off-by: He Zhe <zhe.he@windriver.com>
Cc: stable@vger.kernel.org
Cc: pmladek@suse.com
Cc: sergey.senozhatsky@gmail.com
Cc: rostedt@goodmis.org
---
v2:
Split out the addition of pr_fmt and the unsigned update
v3:
Remove error message for NULL pointer
Add check and error message for over 4G use
v4:
Split each piece into one patch

 kernel/printk/printk.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 9bf5404..06045ab 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1048,7 +1048,12 @@ static void __init log_buf_len_update(unsigned size)
 /* save requested log_buf_len since it's too early to process it */
 static int __init log_buf_len_setup(char *str)
 {
-	unsigned size = memparse(str, &str);
+	unsigned int size;
+
+	if (!str)
+		return -EINVAL;
+
+	size = memparse(str, &str);
 
 	log_buf_len_update(size);
 
-- 
2.7.4

[PATCH v4 2/4] printk: Correct wrong casting

[zhe.he]

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

Correct wrong casting that might cut off the normal output.

Signed-off-by: He Zhe <zhe.he@windriver.com>
Cc: stable@vger.kernel.org
Cc: pmladek@suse.com
Cc: sergey.senozhatsky@gmail.com
Cc: rostedt@goodmis.org
---
 kernel/printk/printk.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 06045ab..c9a0be3 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2356,8 +2356,9 @@ void console_unlock(void)
 		printk_safe_enter_irqsave(flags);
 		raw_spin_lock(&logbuf_lock);
 		if (console_seq < log_first_seq) {
-			len = sprintf(text, "** %u printk messages dropped **\n",
-				      (unsigned)(log_first_seq - console_seq));
+			len = sprintf(text,
+				      "** %llu printk messages dropped **\n",
+				      log_first_seq - console_seq);
 
 			/* messages are gone, move to first one */
 			console_seq = log_first_seq;
-- 
2.7.4

[PATCH v4 3/4] printk: Add KBUILD_MODNAME

[zhe.he]

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

Add KBUILD_MODNAME to make prints more clear.

Signed-off-by: He Zhe <zhe.he@windriver.com>
Cc: pmladek@suse.com
Cc: sergey.senozhatsky@gmail.com
Cc: rostedt@goodmis.org
---
 kernel/printk/printk.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index c9a0be3..b84aac0 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -16,6 +16,8 @@
  *	01Mar01 Andrew Morton
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/tty.h>
-- 
2.7.4

[PATCH v4 4/4] printk: Give error on attempt to set log buffer length to over 4G

[zhe.he]

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

Give explicit error for users who want to use larger log buffer.

Signed-off-by: He Zhe <zhe.he@windriver.com>
Cc: pmladek@suse.com
Cc: sergey.senozhatsky@gmail.com
Cc: rostedt@goodmis.org
---
 kernel/printk/printk.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index b84aac0..5ccfd5d 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1039,18 +1039,23 @@ 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 > UINT_MAX) {
+		size = UINT_MAX;
+		pr_err("log_buf over 4G 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;
-- 
2.7.4

Re: [PATCH v4 3/4] printk: Add KBUILD_MODNAME

[Sergey Senozhatsky]

On (09/29/18 22:48), zhe.he@windriver.com wrote:
>  
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +

Plus this one

---

 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 c9068074dd09..e32f93a2fa84 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2732,7 +2732,7 @@ void register_console(struct console *newcon)
 
 	if (newcon->flags & CON_EXTENDED)
 		if (!nr_ext_console_drivers++)
-			pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
+			pr_info("continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
 
 	if (newcon->flags & CON_PRINTBUFFER) {
 		/*

---

	-ss