[PATCH 5.17 0370/1126] vsprintf: Fix %pK with kptr_restrict == 0

Greg Kroah-Hartman
2022-04-05T08:03:53Z

From: Christophe Leroy <christophe.leroy@csgroup.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@csgroup.eu>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/107476128e59bff11a309b5bf7579a1753a41aca.1645087605.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@kernel.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 7123524a86b8..59f881f36779 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3485,8 +3485,7 @@
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 1ff73ac9e820..fbf261bbea95 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;

@@ -2225,10 +2242,6 @@ 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)
@@ -2457,7 +2470,7 @@ 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':
@@ -2467,16 +2480,9 @@ 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