From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Kees Cook <keescook@chromium.org>
Cc: Helge Deller <deller@gmx.de>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org, linux-ia64@vger.kernel.org,
linux-parisc@vger.kernel.org, linux-arch@vger.kernel.org,
linux-mm@kvack.org,
"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
Paul Mackerras <paulus@samba.org>, Arnd Bergmann <arnd@arndb.de>,
Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH v3 11/12] lkdtm: Fix execute_[user]_location()
Date: Wed, 19 Jan 2022 20:28:54 +0100 [thread overview]
Message-ID: <c635dff6-2bca-3486-014f-12ae00bd1777@csgroup.eu> (raw)
In-Reply-To: <e7793192-6879-490d-1f37-3d6d6908a121@csgroup.eu>
Hi Kees,
Le 17/12/2021 à 12:49, Christophe Leroy a écrit :
> Hi Kees,
>
> Le 17/10/2021 à 14:38, Christophe Leroy a écrit :
>> execute_location() and execute_user_location() intent
>> to copy do_nothing() text and execute it at a new location.
>> However, at the time being it doesn't copy do_nothing() function
>> but do_nothing() function descriptor which still points to the
>> original text. So at the end it still executes do_nothing() at
>> its original location allthough using a copied function descriptor.
>>
>> So, fix that by really copying do_nothing() text and build a new
>> function descriptor by copying do_nothing() function descriptor and
>> updating the target address with the new location.
>>
>> Also fix the displayed addresses by dereferencing do_nothing()
>> function descriptor.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>
> Do you have any comment to this patch and to patch 12 ?
>
> If not, is it ok to get your acked-by ?
Any feedback please, even if it's to say no feedback ?
Many thanks,
Christophe
>
> Thanks
> Christophe
>
>> ---
>> drivers/misc/lkdtm/perms.c | 37 ++++++++++++++++++++++++++++---------
>> 1 file changed, 28 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>> index 035fcca441f0..1cf24c4a79e9 100644
>> --- a/drivers/misc/lkdtm/perms.c
>> +++ b/drivers/misc/lkdtm/perms.c
>> @@ -44,19 +44,34 @@ static noinline void do_overwritten(void)
>> return;
>> }
>> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>> +{
>> + if (!have_function_descriptors())
>> + return dst;
>> +
>> + memcpy(fdesc, do_nothing, sizeof(*fdesc));
>> + fdesc->addr = (unsigned long)dst;
>> + barrier();
>> +
>> + return fdesc;
>> +}
>> +
>> static noinline void execute_location(void *dst, bool write)
>> {
>> - void (*func)(void) = dst;
>> + void (*func)(void);
>> + func_desc_t fdesc;
>> + void *do_nothing_text = dereference_function_descriptor(do_nothing);
>> - pr_info("attempting ok execution at %px\n", do_nothing);
>> + pr_info("attempting ok execution at %px\n", do_nothing_text);
>> do_nothing();
>> if (write == CODE_WRITE) {
>> - memcpy(dst, do_nothing, EXEC_SIZE);
>> + memcpy(dst, do_nothing_text, EXEC_SIZE);
>> flush_icache_range((unsigned long)dst,
>> (unsigned long)dst + EXEC_SIZE);
>> }
>> - pr_info("attempting bad execution at %px\n", func);
>> + pr_info("attempting bad execution at %px\n", dst);
>> + func = setup_function_descriptor(&fdesc, dst);
>> func();
>> pr_err("FAIL: func returned\n");
>> }
>> @@ -66,16 +81,19 @@ static void execute_user_location(void *dst)
>> int copied;
>> /* Intentionally crossing kernel/user memory boundary. */
>> - void (*func)(void) = dst;
>> + void (*func)(void);
>> + func_desc_t fdesc;
>> + void *do_nothing_text = dereference_function_descriptor(do_nothing);
>> - pr_info("attempting ok execution at %px\n", do_nothing);
>> + pr_info("attempting ok execution at %px\n", do_nothing_text);
>> do_nothing();
>> - copied = access_process_vm(current, (unsigned long)dst, do_nothing,
>> + copied = access_process_vm(current, (unsigned long)dst,
>> do_nothing_text,
>> EXEC_SIZE, FOLL_WRITE);
>> if (copied < EXEC_SIZE)
>> return;
>> - pr_info("attempting bad execution at %px\n", func);
>> + pr_info("attempting bad execution at %px\n", dst);
>> + func = setup_function_descriptor(&fdesc, dst);
>> func();
>> pr_err("FAIL: func returned\n");
>> }
>> @@ -153,7 +171,8 @@ void lkdtm_EXEC_VMALLOC(void)
>> void lkdtm_EXEC_RODATA(void)
>> {
>> - execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
>> +
>> execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing),
>>
>> + CODE_AS_IS);
>> }
>> void lkdtm_EXEC_USERSPACE(void)
>>
next prev parent reply other threads:[~2022-01-19 19:29 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-17 12:38 [PATCH v3 00/12] Fix LKDTM for PPC64/IA64/PARISC Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 01/12] powerpc: Move and rename func_descr_t Christophe Leroy
2021-10-18 5:58 ` Nicholas Piggin
2022-02-11 0:51 ` Kees Cook
2021-10-17 12:38 ` [PATCH v3 02/12] powerpc: Use 'struct func_desc' instead of 'struct ppc64_opd_entry' Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 03/12] powerpc: Remove " Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 04/12] powerpc: Prepare func_desc_t for refactorisation Christophe Leroy
2021-10-18 6:27 ` Nicholas Piggin
2021-10-18 7:08 ` Christophe Leroy
2022-02-11 0:54 ` Kees Cook
2022-02-11 7:39 ` Segher Boessenkool
2022-02-14 10:30 ` Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 05/12] ia64: Rename 'ip' to 'addr' in 'struct fdesc' Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 06/12] asm-generic: Define CONFIG_HAVE_FUNCTION_DESCRIPTORS Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 07/12] asm-generic: Define 'func_desc_t' to commonly describe function descriptors Christophe Leroy
2021-10-18 6:29 ` Nicholas Piggin
2021-10-18 7:07 ` Christophe Leroy
2021-10-18 9:16 ` Nicholas Piggin
2021-10-17 12:38 ` [PATCH v3 08/12] asm-generic: Refactor dereference_[kernel]_function_descriptor() Christophe Leroy
2022-02-10 10:30 ` Michael Ellerman
2022-02-11 0:56 ` Kees Cook
2022-02-14 10:32 ` Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 09/12] lkdtm: Force do_nothing() out of line Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 10/12] lkdtm: Really write into kernel text in WRITE_KERN Christophe Leroy
2021-10-17 12:38 ` [PATCH v3 11/12] lkdtm: Fix execute_[user]_location() Christophe Leroy
2021-12-17 11:49 ` Christophe Leroy
2021-12-17 17:12 ` Helge Deller
2022-01-19 19:28 ` Christophe Leroy [this message]
2022-01-19 22:00 ` Kees Cook
2022-02-11 1:01 ` Kees Cook
2021-10-17 12:38 ` [PATCH v3 12/12] lkdtm: Add a test for function descriptors protection Christophe Leroy
2022-02-11 1:09 ` Kees Cook
2022-02-14 10:34 ` Christophe Leroy
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