Merge tag 'printk-for-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

Pull printk updates from Petr Mladek:

 - Fix off-by-one error when calculating messages that might fit into
   kmsg buffer. It causes occasional omitting of the last message.

 - Add missing pointer check in %pD format modifier handling.

 - Some clean up

* tag 'printk-for-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  ABI: Update dev-kmsg documentation to match current kernel behaviour
  printk: Replace strncmp() with str_has_prefix()
  lib/test_printf: Remove obvious comments from %pd and %pD tests
  lib/test_printf: Add test of null/invalid pointer dereference for dentry
  vsprintf: Prevent crash when dereferencing invalid pointers for %pD
  printk: Do not lose last line in kmsg buffer dump

2 files changed, 15 insertions, 3 deletions

diff --git a/lib/test_printf.c b/lib/test_printf.c
index 944eb50f3862..5d94cbff2120 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -455,6 +455,11 @@ dentry(void)
 	test("foo", "%pd", &test_dentry[0]);
 	test("foo", "%pd2", &test_dentry[0]);
 
+	test("(null)", "%pd", NULL);
+	test("(efault)", "%pd", PTR_INVALID);
+	test("(null)", "%pD", NULL);
+	test("(efault)", "%pD", PTR_INVALID);
+
 	test("romeo", "%pd", &test_dentry[3]);
 	test("alfa/romeo", "%pd2", &test_dentry[3]);
 	test("bravo/alfa/romeo", "%pd3", &test_dentry[3]);
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index b0967cf17137..e78017a3e1bd 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -869,6 +869,15 @@ char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_sp
 	return widen_string(buf, n, end, spec);
 }
 
+static noinline_for_stack
+char *file_dentry_name(char *buf, char *end, const struct file *f,
+			struct printf_spec spec, const char *fmt)
+{
+	if (check_pointer(&buf, end, f, spec))
+		return buf;
+
+	return dentry_name(buf, end, f->f_path.dentry, spec, fmt);
+}
 #ifdef CONFIG_BLOCK
 static noinline_for_stack
 char *bdev_name(char *buf, char *end, struct block_device *bdev,
@@ -2166,9 +2175,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 	case 'C':
 		return clock(buf, end, ptr, spec, fmt);
 	case 'D':
-		return dentry_name(buf, end,
-				   ((const struct file *)ptr)->f_path.dentry,
-				   spec, fmt);
+		return file_dentry_name(buf, end, ptr, spec, fmt);
 #ifdef CONFIG_BLOCK
 	case 'g':
 		return bdev_name(buf, end, ptr, spec, fmt);