diff mbox series

[v7,2/4] uaccess: always export _copy_[from|to]_user with CONFIG_RUST

Message ID 20240528-alice-mm-v7-2-78222c31b8f4@google.com (mailing list archive)
State New
Headers show
Series Memory management patches needed by Rust Binder | expand

Commit Message

Alice Ryhl May 28, 2024, 2:58 p.m. UTC 
From: Arnd Bergmann <arnd@arndb.de>

Rust code needs to be able to access _copy_from_user and _copy_to_user
so that it can skip the check_copy_size check in cases where the length
is known at compile-time, mirroring the logic for when C code will skip
check_copy_size. To do this, we ensure that exported versions of these
methods are available when CONFIG_RUST is enabled.

Alice has verified that this patch passes the CONFIG_TEST_USER_COPY test
on x86 using the Android cuttlefish emulator.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
 include/linux/uaccess.h | 46 ++++++++++++++++++++++++++++++++--------------
 lib/usercopy.c          | 30 ++++--------------------------
 2 files changed, 36 insertions(+), 40 deletions(-)

Comments

Andrew Morton June 11, 2024, 9:44 p.m. UTC | #1 
On Tue, 28 May 2024 14:58:03 +0000 Alice Ryhl <aliceryhl@google.com> wrote:

> Rust code needs to be able to access _copy_from_user and _copy_to_user
> so that it can skip the check_copy_size check in cases where the length
> is known at compile-time, mirroring the logic for when C code will skip
> check_copy_size. To do this, we ensure that exported versions of these
> methods are available when CONFIG_RUST is enabled.
> 
> Alice has verified that this patch passes the CONFIG_TEST_USER_COPY test
> on x86 using the Android cuttlefish emulator.
> 
> ...
>
>  include/linux/uaccess.h | 46 ++++++++++++++++++++++++++++++++--------------
>  lib/usercopy.c          | 30 ++++--------------------------
>  2 files changed, 36 insertions(+), 40 deletions(-)

Acked-by: Andrew Morton <akpm@linux-foundation.org>
Sasha Levin Sept. 22, 2024, 7:08 a.m. UTC | #2 
On Tue, May 28, 2024 at 02:58:03PM +0000, Alice Ryhl wrote:
>From: Arnd Bergmann <arnd@arndb.de>
>
>Rust code needs to be able to access _copy_from_user and _copy_to_user
>so that it can skip the check_copy_size check in cases where the length
>is known at compile-time, mirroring the logic for when C code will skip
>check_copy_size. To do this, we ensure that exported versions of these
>methods are available when CONFIG_RUST is enabled.
>
>Alice has verified that this patch passes the CONFIG_TEST_USER_COPY test
>on x86 using the Android cuttlefish emulator.

Hi folks,

I've noticed a build failure using GCC 9.5.0 on arm64 allmodconfig
builds:

In file included from ./arch/arm64/include/asm/preempt.h:6,
                  from ./include/linux/preempt.h:79,
                  from ./include/linux/alloc_tag.h:11,
                  from ./include/linux/percpu.h:5,
                  from ./include/linux/context_tracking_state.h:5,
                  from ./include/linux/hardirq.h:5,
                  from drivers/net/ethernet/mellanox/mlx4/cq.c:37:
In function 'check_copy_size',
     inlined from 'mlx4_init_user_cqes' at ./include/linux/uaccess.h:203:7:
./include/linux/thread_info.h:244:4: error: call to '__bad_copy_from' declared with attribute error: copy source size is too small
   244 |    __bad_copy_from();
       |    ^~~~~~~~~~~~~~~~~
make[7]: *** [scripts/Makefile.build:244: drivers/net/ethernet/mellanox/mlx4/cq.o] Error 1

I do not have CONFIG_RUST enabled in those builds.

I've bisected the issue (twice!) and bisection points to this patch
which landed upstream as 1f9a8286bc0c ("uaccess: always export
_copy_[from|to]_user with CONFIG_RUST").

Reverting said commit on top of Linus's tree fixes the build breakage.
Arnd Bergmann Sept. 22, 2024, 7:52 a.m. UTC | #3 
On Sun, Sep 22, 2024, at 07:08, Sasha Levin wrote:
> On Tue, May 28, 2024 at 02:58:03PM +0000, Alice Ryhl wrote:
>>From: Arnd Bergmann <arnd@arndb.de>
>>
>>Rust code needs to be able to access _copy_from_user and _copy_to_user
>>so that it can skip the check_copy_size check in cases where the length
>>is known at compile-time, mirroring the logic for when C code will skip
>>check_copy_size. To do this, we ensure that exported versions of these
>>methods are available when CONFIG_RUST is enabled.
>>
>>Alice has verified that this patch passes the CONFIG_TEST_USER_COPY test
>>on x86 using the Android cuttlefish emulator.
>
> Hi folks,
>
> I've noticed a build failure using GCC 9.5.0 on arm64 allmodconfig
> builds:
>
> In file included from ./arch/arm64/include/asm/preempt.h:6,
>                   from ./include/linux/preempt.h:79,
>                   from ./include/linux/alloc_tag.h:11,
>                   from ./include/linux/percpu.h:5,
>                   from ./include/linux/context_tracking_state.h:5,
>                   from ./include/linux/hardirq.h:5,
>                   from drivers/net/ethernet/mellanox/mlx4/cq.c:37:
> In function 'check_copy_size',
>      inlined from 'mlx4_init_user_cqes' at 
> ./include/linux/uaccess.h:203:7:
> ./include/linux/thread_info.h:244:4: error: call to '__bad_copy_from' 
> declared with attribute error: copy source size is too small
>    244 |    __bad_copy_from();
>        |    ^~~~~~~~~~~~~~~~~
> make[7]: *** [scripts/Makefile.build:244: 
> drivers/net/ethernet/mellanox/mlx4/cq.o] Error 1
>
> I do not have CONFIG_RUST enabled in those builds.
>
> I've bisected the issue (twice!) and bisection points to this patch
> which landed upstream as 1f9a8286bc0c ("uaccess: always export
> _copy_[from|to]_user with CONFIG_RUST").
>
> Reverting said commit on top of Linus's tree fixes the build breakage.

Right, it seems we still need the fix I posted in

https://lore.kernel.org/lkml/20230418114730.3674657-1-arnd@kernel.org/

Tariq, should I resend this with your Reviewed-by, or can you
apply it from the old version and make sure it finds its way
into mainline and 6.11?

     Arnd
Sasha Levin Sept. 22, 2024, 1:16 p.m. UTC | #4 
On Sun, Sep 22, 2024 at 07:52:34AM +0000, Arnd Bergmann wrote:
>On Sun, Sep 22, 2024, at 07:08, Sasha Levin wrote:
>> On Tue, May 28, 2024 at 02:58:03PM +0000, Alice Ryhl wrote:
>>>From: Arnd Bergmann <arnd@arndb.de>
>>>
>>>Rust code needs to be able to access _copy_from_user and _copy_to_user
>>>so that it can skip the check_copy_size check in cases where the length
>>>is known at compile-time, mirroring the logic for when C code will skip
>>>check_copy_size. To do this, we ensure that exported versions of these
>>>methods are available when CONFIG_RUST is enabled.
>>>
>>>Alice has verified that this patch passes the CONFIG_TEST_USER_COPY test
>>>on x86 using the Android cuttlefish emulator.
>>
>> Hi folks,
>>
>> I've noticed a build failure using GCC 9.5.0 on arm64 allmodconfig
>> builds:
>>
>> In file included from ./arch/arm64/include/asm/preempt.h:6,
>>                   from ./include/linux/preempt.h:79,
>>                   from ./include/linux/alloc_tag.h:11,
>>                   from ./include/linux/percpu.h:5,
>>                   from ./include/linux/context_tracking_state.h:5,
>>                   from ./include/linux/hardirq.h:5,
>>                   from drivers/net/ethernet/mellanox/mlx4/cq.c:37:
>> In function 'check_copy_size',
>>      inlined from 'mlx4_init_user_cqes' at
>> ./include/linux/uaccess.h:203:7:
>> ./include/linux/thread_info.h:244:4: error: call to '__bad_copy_from'
>> declared with attribute error: copy source size is too small
>>    244 |    __bad_copy_from();
>>        |    ^~~~~~~~~~~~~~~~~
>> make[7]: *** [scripts/Makefile.build:244:
>> drivers/net/ethernet/mellanox/mlx4/cq.o] Error 1
>>
>> I do not have CONFIG_RUST enabled in those builds.
>>
>> I've bisected the issue (twice!) and bisection points to this patch
>> which landed upstream as 1f9a8286bc0c ("uaccess: always export
>> _copy_[from|to]_user with CONFIG_RUST").
>>
>> Reverting said commit on top of Linus's tree fixes the build breakage.
>
>Right, it seems we still need the fix I posted in
>
>https://lore.kernel.org/lkml/20230418114730.3674657-1-arnd@kernel.org/
>
>Tariq, should I resend this with your Reviewed-by, or can you
>apply it from the old version and make sure it finds its way
>into mainline and 6.11?

The patch above fixes the build issue for me, thanks!
diff mbox series

Patch

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 3064314f4832..d8e4105a2f21 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -5,6 +5,7 @@ 
 #include <linux/fault-inject-usercopy.h>
 #include <linux/instrumented.h>
 #include <linux/minmax.h>
+#include <linux/nospec.h>
 #include <linux/sched.h>
 #include <linux/thread_info.h>
 
@@ -138,13 +139,26 @@  __copy_to_user(void __user *to, const void *from, unsigned long n)
 	return raw_copy_to_user(to, from, n);
 }
 
-#ifdef INLINE_COPY_FROM_USER
+/*
+ * Architectures that #define INLINE_COPY_TO_USER use this function
+ * directly in the normal copy_to/from_user(), the other ones go
+ * through an extern _copy_to/from_user(), which expands the same code
+ * here.
+ *
+ * Rust code always uses the extern definition.
+ */
 static inline __must_check unsigned long
-_copy_from_user(void *to, const void __user *from, unsigned long n)
+_inline_copy_from_user(void *to, const void __user *from, unsigned long n)
 {
 	unsigned long res = n;
 	might_fault();
 	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
+		/*
+		 * Ensure that bad access_ok() speculation will not
+		 * lead to nasty side effects *after* the copy is
+		 * finished:
+		 */
+		barrier_nospec();
 		instrument_copy_from_user_before(to, from, n);
 		res = raw_copy_from_user(to, from, n);
 		instrument_copy_from_user_after(to, from, n, res);
@@ -153,14 +167,11 @@  _copy_from_user(void *to, const void __user *from, unsigned long n)
 		memset(to + (n - res), 0, res);
 	return res;
 }
-#else
 extern __must_check unsigned long
 _copy_from_user(void *, const void __user *, unsigned long);
-#endif
 
-#ifdef INLINE_COPY_TO_USER
 static inline __must_check unsigned long
-_copy_to_user(void __user *to, const void *from, unsigned long n)
+_inline_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
 	might_fault();
 	if (should_fail_usercopy())
@@ -171,25 +182,32 @@  _copy_to_user(void __user *to, const void *from, unsigned long n)
 	}
 	return n;
 }
-#else
 extern __must_check unsigned long
 _copy_to_user(void __user *, const void *, unsigned long);
-#endif
 
 static __always_inline unsigned long __must_check
 copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	if (check_copy_size(to, n, false))
-		n = _copy_from_user(to, from, n);
-	return n;
+	if (!check_copy_size(to, n, false))
+		return n;
+#ifdef INLINE_COPY_FROM_USER
+	return _inline_copy_from_user(to, from, n);
+#else
+	return _copy_from_user(to, from, n);
+#endif
 }
 
 static __always_inline unsigned long __must_check
 copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	if (check_copy_size(from, n, true))
-		n = _copy_to_user(to, from, n);
-	return n;
+	if (!check_copy_size(from, n, true))
+		return n;
+
+#ifdef INLINE_COPY_TO_USER
+	return _inline_copy_to_user(to, from, n);
+#else
+	return _copy_to_user(to, from, n);
+#endif
 }
 
 #ifndef copy_mc_to_kernel
diff --git a/lib/usercopy.c b/lib/usercopy.c
index 499a7a7d54db..7b17b83c8042 100644
--- a/lib/usercopy.c
+++ b/lib/usercopy.c
@@ -12,40 +12,18 @@ 
 
 /* out-of-line parts */
 
-#ifndef INLINE_COPY_FROM_USER
+#if !defined(INLINE_COPY_FROM_USER) || defined(CONFIG_RUST)
 unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	unsigned long res = n;
-	might_fault();
-	if (!should_fail_usercopy() && likely(access_ok(from, n))) {
-		/*
-		 * Ensure that bad access_ok() speculation will not
-		 * lead to nasty side effects *after* the copy is
-		 * finished:
-		 */
-		barrier_nospec();
-		instrument_copy_from_user_before(to, from, n);
-		res = raw_copy_from_user(to, from, n);
-		instrument_copy_from_user_after(to, from, n, res);
-	}
-	if (unlikely(res))
-		memset(to + (n - res), 0, res);
-	return res;
+	return _inline_copy_from_user(to, from, n);
 }
 EXPORT_SYMBOL(_copy_from_user);
 #endif
 
-#ifndef INLINE_COPY_TO_USER
+#if !defined(INLINE_COPY_TO_USER) || defined(CONFIG_RUST)
 unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	might_fault();
-	if (should_fail_usercopy())
-		return n;
-	if (likely(access_ok(to, n))) {
-		instrument_copy_to_user(to, from, n);
-		n = raw_copy_to_user(to, from, n);
-	}
-	return n;
+	return _inline_copy_to_user(to, from, n);
 }
 EXPORT_SYMBOL(_copy_to_user);
 #endif