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vsprintf: Fix %pK with kptr_restrict == 0 

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: 5ead723a20 ("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
This commit is contained in:
Christophe Leroy 2022-02-17 09:49:59 +01:00 committed by Petr Mladek
parent a5a763b2b2
commit 8484291132
2 changed files with 22 additions and 17 deletions
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3
Documentation/admin-guide/kernel-parameters.txt
View File

@ -3491,8 +3491,7 @@
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.

36
lib/vsprintf.c
View File

@ -53,6 +53,10 @@
#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;
@ -848,6 +852,19 @@ 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
@ -857,7 +874,7 @@ 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;
@ -2233,10 +2250,6 @@ 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)
@ -2465,7 +2478,7 @@ 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':
@ -2475,16 +2488,9 @@ 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);
}
/*