Commit 84842911 authored by Christophe Leroy's avatar Christophe Leroy Committed by Petr Mladek
Browse files

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: 5ead723a ("lib/vsprintf: no_hash_pointers prints all addresses as unhashed")
Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/107476128e59bff11a309b5bf7579a1753a41aca.1645087605.git.christophe.leroy@csgroup.eu
parent a5a763b2

Documentation/admin-guide/kernel-parameters.txt

+1 −2
Original line number Diff line number Diff line
@@ -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.

lib/vsprintf.c

+21 −15
Original line number Diff line number Diff line
@@ -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);

}



/*