* [PATCH] vsprintf: Fix %pK with kptr_restrict == 0
@ 2022-01-27 11:11 Christophe Leroy
2022-02-08 13:51 ` Petr Mladek
0 siblings, 1 reply; 3+ messages in thread
From: Christophe Leroy @ 2022-01-27 11:11 UTC (permalink / raw)
To: Petr Mladek, Steven Rostedt, Sergey Senozhatsky, Andy Shevchenko,
Rasmus Villemoes
Cc: Christophe Leroy, linux-kernel, linux-mm
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: 1ac2f9789c4b ("vsprintf: Consistent %pK handling for kptr_restrict == 0")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
lib/vsprintf.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3b8129dd374c..9c60d6e1a0d6 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -848,6 +848,10 @@ static char *ptr_to_id(char *buf, char *end, const void *ptr,
return pointer_string(buf, end, (const void *)hashval, spec);
}
+/* Disable pointer hashing if requested */
+bool no_hash_pointers __ro_after_init;
+EXPORT_SYMBOL_GPL(no_hash_pointers);
+
int kptr_restrict __read_mostly;
static noinline_for_stack
@@ -857,6 +861,8 @@ char *restricted_pointer(char *buf, char *end, const void *ptr,
switch (kptr_restrict) {
case 0:
/* Handle as %p, hash and do _not_ leak addresses. */
+ if (unlikely(no_hash_pointers))
+ break;
return ptr_to_id(buf, end, ptr, spec);
case 1: {
const struct cred *cred;
@@ -2223,10 +2229,6 @@ 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)
--
2.33.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] vsprintf: Fix %pK with kptr_restrict == 0
2022-01-27 11:11 [PATCH] vsprintf: Fix %pK with kptr_restrict == 0 Christophe Leroy
@ 2022-02-08 13:51 ` Petr Mladek
2022-02-09 11:53 ` Andy Shevchenko
0 siblings, 1 reply; 3+ messages in thread
From: Petr Mladek @ 2022-02-08 13:51 UTC (permalink / raw)
To: Christophe Leroy
Cc: Steven Rostedt, Sergey Senozhatsky, Andy Shevchenko,
Rasmus Villemoes, linux-kernel, linux-mm, Kees Cook,
Linus Torvalds
Adding Kees and Linus in Cc because it modifies %pK behavior.
On Thu 2022-01-27 11:11:02, Christophe Leroy wrote:
> 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.
Good catch!
BTW: The behavior is strange also when kptr_restrict == 1. It allways
prints non-hashed pointers for user space adresses. It means that
it is less restrictive than kptr_restrict == 0 by default when
no_hash_pointers == 0. It is probably not a big deal but...
> ---
> lib/vsprintf.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 3b8129dd374c..9c60d6e1a0d6 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -857,6 +861,8 @@ char *restricted_pointer(char *buf, char *end, const void *ptr,
> switch (kptr_restrict) {
> case 0:
> /* Handle as %p, hash and do _not_ leak addresses. */
> + if (unlikely(no_hash_pointers))
> + break;
> return ptr_to_id(buf, end, ptr, spec);
This is a twisted duplication of the following code from pointer():
static noinline_for_stack
char *pointer(const char *fmt, char *buf, char *end, 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);
else
return ptr_to_id(buf, end, ptr, spec);
}
Instead, I would create:
/*
* default is to _not_ leak addresses, so hash before printing,
* unless no_hash_pointers is specified on the command line.
*/
static noinline_for_stack
char *default_pointer(const char *fmt, char *buf, char *end, void *ptr,
struct printf_spec spec)
{
if (unlikely(no_hash_pointers))
return pointer_string(buf, end, ptr, spec);
return ptr_to_id(buf, end, ptr, spec);
}
and use it in both hash_pointer() and pointer().
And I would use is also for kptr_restrict == 1. But it probably
should be done in a separate patch and should be acked by Kees.
> case 1: {
> const struct cred *cred;
Best Regards,
Petr
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] vsprintf: Fix %pK with kptr_restrict == 0
2022-02-08 13:51 ` Petr Mladek
@ 2022-02-09 11:53 ` Andy Shevchenko
0 siblings, 0 replies; 3+ messages in thread
From: Andy Shevchenko @ 2022-02-09 11:53 UTC (permalink / raw)
To: Petr Mladek
Cc: Christophe Leroy, Steven Rostedt, Sergey Senozhatsky,
Rasmus Villemoes, linux-kernel, linux-mm, Kees Cook,
Linus Torvalds
On Tue, Feb 08, 2022 at 02:51:39PM +0100, Petr Mladek wrote:
> On Thu 2022-01-27 11:11:02, Christophe Leroy wrote:
...
> Instead, I would create:
>
> /*
> * default is to _not_ leak addresses, so hash before printing,
> * unless no_hash_pointers is specified on the command line.
> */
> static noinline_for_stack
> char *default_pointer(const char *fmt, char *buf, char *end, void *ptr,
> struct printf_spec spec)
> {
> if (unlikely(no_hash_pointers))
> return pointer_string(buf, end, ptr, spec);
>
> return ptr_to_id(buf, end, ptr, spec);
> }
>
> and use it in both hash_pointer() and pointer().
I like this idea.
--
With Best Regards,
Andy Shevchenko
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-02-09 12:01 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-01-27 11:11 [PATCH] vsprintf: Fix %pK with kptr_restrict == 0 Christophe Leroy
2022-02-08 13:51 ` Petr Mladek
2022-02-09 11:53 ` Andy Shevchenko
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.