Merge tag 'printk-for-5.2-fixes' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

Pull printk fixup from Petr Mladek:
 "Replace the problematic probe_kernel_read() with original simple
  pointer checks in vsprintf()"

* tag 'printk-for-5.2-fixes' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  vsprintf: Do not break early boot with probing addresses

1 files changed, 4 insertions, 7 deletions

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 7b0a6140bfad..2f003cfe340e 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -628,19 +628,16 @@ static char *error_string(char *buf, char *end, const char *s,
 }
 
 /*
- * This is not a fool-proof test. 99% of the time that this will fault is
- * due to a bad pointer, not one that crosses into bad memory. Just test
- * the address to make sure it doesn't fault due to a poorly added printk
- * during debugging.
+ * Do not call any complex external code here. Nested printk()/vsprintf()
+ * might cause infinite loops. Failures might break printk() and would
+ * be hard to debug.
  */
 static const char *check_pointer_msg(const void *ptr)
 {
-	char byte;
-
 	if (!ptr)
 		return "(null)";
 
-	if (probe_kernel_address(ptr, byte))
+	if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
 		return "(efault)";
 
 	return NULL;