linux-kernel - [PATCH 5.16 0348/1017] vsprintf: Fix %pK with kptr

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Date:   Tue,  5 Apr 2022 09:21:01 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Petr Mladek <pmladek@...e.com>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.16 0348/1017] vsprintf: Fix %pK with kptr_restrict == 0

From: Christophe Leroy <christophe.leroy@...roup.eu>

[ Upstream commit 84842911322fc6a02a03ab9e728a48c691fe3efd ]

Although kptr_restrict is set to 0 and the kernel is booted with
no_hash_pointers parameter, the content of /proc/vmallocinfo is
lacking the real addresses.

  / # cat /proc/vmallocinfo
  0x(ptrval)-0x(ptrval)    8192 load_module+0xc0c/0x2c0c pages=1 vmalloc
  0x(ptrval)-0x(ptrval)   12288 start_kernel+0x4e0/0x690 pages=2 vmalloc
  0x(ptrval)-0x(ptrval)   12288 start_kernel+0x4e0/0x690 pages=2 vmalloc
  0x(ptrval)-0x(ptrval)    8192 _mpic_map_mmio.constprop.0+0x20/0x44 phys=0x80041000 ioremap
  0x(ptrval)-0x(ptrval)   12288 _mpic_map_mmio.constprop.0+0x20/0x44 phys=0x80041000 ioremap
    ...

According to the documentation for /proc/sys/kernel/, %pK is
equivalent to %p when kptr_restrict is set to 0.

Fixes: 5ead723a20e0 ("lib/vsprintf: no_hash_pointers prints all addresses as unhashed")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Reviewed-by: Petr Mladek <pmladek@...e.com>
Signed-off-by: Petr Mladek <pmladek@...e.com>
Link: https://lore.kernel.org/r/107476128e59bff11a309b5bf7579a1753a41aca.1645087605.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../admin-guide/kernel-parameters.txt         |  3 +-
 lib/vsprintf.c                                | 36 +++++++++++--------
 2 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 391b3f9055fe..3e513d69e9de 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3476,8 +3476,7 @@
 			difficult since unequal pointers can no longer be
 			compared.  However, if this command-line option is
 			specified, then all normal pointers will have their true
-			value printed.  Pointers printed via %pK may still be
-			hashed.  This option should only be specified when
+			value printed. This option should only be specified when
 			debugging the kernel.  Please do not use on production
 			kernels.
 
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 01e61c85f274..937dd643008d 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -54,6 +54,10 @@
 #include <linux/string_helpers.h>
 #include "kstrtox.h"
 
+/* Disable pointer hashing if requested */
+bool no_hash_pointers __ro_after_init;
+EXPORT_SYMBOL_GPL(no_hash_pointers);
+
 static noinline unsigned long long simple_strntoull(const char *startp, size_t max_chars, char **endp, unsigned int base)
 {
 	const char *cp;
@@ -849,6 +853,19 @@ static char *ptr_to_id(char *buf, char *end, const void *ptr,
 	return pointer_string(buf, end, (const void *)hashval, spec);
 }
 
+static char *default_pointer(char *buf, char *end, const void *ptr,
+			     struct printf_spec spec)
+{
+	/*
+	 * default is to _not_ leak addresses, so hash before printing,
+	 * unless no_hash_pointers is specified on the command line.
+	 */
+	if (unlikely(no_hash_pointers))
+		return pointer_string(buf, end, ptr, spec);
+
+	return ptr_to_id(buf, end, ptr, spec);
+}
+
 int kptr_restrict __read_mostly;
 
 static noinline_for_stack
@@ -858,7 +875,7 @@ char *restricted_pointer(char *buf, char *end, const void *ptr,
 	switch (kptr_restrict) {
 	case 0:
 		/* Handle as %p, hash and do _not_ leak addresses. */
-		return ptr_to_id(buf, end, ptr, spec);
+		return default_pointer(buf, end, ptr, spec);
 	case 1: {
 		const struct cred *cred;
 
@@ -2235,10 +2252,6 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
 	return widen_string(buf, buf - buf_start, end, spec);
 }
 
-/* Disable pointer hashing if requested */
-bool no_hash_pointers __ro_after_init;
-EXPORT_SYMBOL_GPL(no_hash_pointers);
-
 int __init no_hash_pointers_enable(char *str)
 {
 	if (no_hash_pointers)
@@ -2467,7 +2480,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 	case 'e':
 		/* %pe with a non-ERR_PTR gets treated as plain %p */
 		if (!IS_ERR(ptr))
-			break;
+			return default_pointer(buf, end, ptr, spec);
 		return err_ptr(buf, end, ptr, spec);
 	case 'u':
 	case 'k':
@@ -2477,16 +2490,9 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 		default:
 			return error_string(buf, end, "(einval)", spec);
 		}
+	default:
+		return default_pointer(buf, end, ptr, spec);
 	}
-
-	/*
-	 * default is to _not_ leak addresses, so hash before printing,
-	 * unless no_hash_pointers is specified on the command line.
-	 */
-	if (unlikely(no_hash_pointers))
-		return pointer_string(buf, end, ptr, spec);
-	else
-		return ptr_to_id(buf, end, ptr, spec);
 }
 
 /*
-- 
2.34.1