Allthough masked_user_access_begin() is to only be used when reading
data from user at the moment, introduce masked_user_read_access_begin()
and masked_user_write_access_begin() in order to match
user_read_access_begin() and user_write_access_begin().
That means masked_user_read_access_begin() is used when user memory is
exclusively read during the window, masked_user_write_access_begin()
is used when user memory is exclusively writen during the window,
masked_user_access_begin() remains and is used when both reads and
writes are performed during the open window. Each of them is expected
to be terminated by the matching user_read_access_end(),
user_write_access_end() and user_access_end().
Have them default to masked_user_access_begin() when they are
not defined.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v3: Rebased on top of v6.18-rc1 ==> change in net/core/scm.c
v2: Added more explanations in the commit message following comments received.
---
fs/select.c | 2 +-
include/linux/uaccess.h | 7 +++++++
kernel/futex/futex.h | 4 ++--
lib/strncpy_from_user.c | 2 +-
lib/strnlen_user.c | 2 +-
net/core/scm.c | 2 +-
6 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/fs/select.c b/fs/select.c
index 082cf60c7e235..36db0359388c8 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -777,7 +777,7 @@ static inline int get_sigset_argpack(struct sigset_argpack *to,
// the path is hot enough for overhead of copy_from_user() to matter
if (from) {
if (can_do_masked_user_access())
- from = masked_user_access_begin(from);
+ from = masked_user_read_access_begin(from);
else if (!user_read_access_begin(from, sizeof(*from)))
return -EFAULT;
unsafe_get_user(to->p, &from->p, Efault);
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 1beb5b395d81d..aa48d5415d32f 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -41,6 +41,13 @@
#define mask_user_address(src) (src)
#endif
+#ifndef masked_user_write_access_begin
+#define masked_user_write_access_begin masked_user_access_begin
+#endif
+#ifndef masked_user_read_access_begin
+#define masked_user_read_access_begin masked_user_access_begin
+#endif
+
/*
* Architectures should provide two primitives (raw_copy_{to,from}_user())
* and get rid of their private instances of copy_{to,from}_user() and
diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index 2cd57096c38e1..a1120a318c186 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -303,7 +303,7 @@ static __always_inline int futex_get_value(u32 *dest, u32 __user *from)
u32 val;
if (can_do_masked_user_access())
- from = masked_user_access_begin(from);
+ from = masked_user_read_access_begin(from);
else if (!user_read_access_begin(from, sizeof(*from)))
return -EFAULT;
unsafe_get_user(val, from, Efault);
@@ -318,7 +318,7 @@ static __always_inline int futex_get_value(u32 *dest, u32 __user *from)
static __always_inline int futex_put_value(u32 val, u32 __user *to)
{
if (can_do_masked_user_access())
- to = masked_user_access_begin(to);
+ to = masked_user_write_access_begin(to);
else if (!user_write_access_begin(to, sizeof(*to)))
return -EFAULT;
unsafe_put_user(val, to, Efault);
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 6dc234913dd58..5bb752ff7c61b 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -126,7 +126,7 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
if (can_do_masked_user_access()) {
long retval;
- src = masked_user_access_begin(src);
+ src = masked_user_read_access_begin(src);
retval = do_strncpy_from_user(dst, src, count, count);
user_read_access_end();
return retval;
diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
index 6e489f9e90f15..4a6574b67f824 100644
--- a/lib/strnlen_user.c
+++ b/lib/strnlen_user.c
@@ -99,7 +99,7 @@ long strnlen_user(const char __user *str, long count)
if (can_do_masked_user_access()) {
long retval;
- str = masked_user_access_begin(str);
+ str = masked_user_read_access_begin(str);
retval = do_strnlen_user(str, count, count);
user_read_access_end();
return retval;
diff --git a/net/core/scm.c b/net/core/scm.c
index 66eaee783e8be..4a65f9baa87e7 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -274,7 +274,7 @@ int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
check_object_size(data, cmlen - sizeof(*cm), true);
if (can_do_masked_user_access())
- cm = masked_user_access_begin(cm);
+ cm = masked_user_write_access_begin(cm);
else if (!user_write_access_begin(cm, cmlen))
goto efault;
--
2.49.0On Fri, Oct 17 2025 at 12:20, Christophe Leroy wrote:
> Allthough masked_user_access_begin() is to only be used when reading
> data from user at the moment, introduce masked_user_read_access_begin()
> and masked_user_write_access_begin() in order to match
> user_read_access_begin() and user_write_access_begin().
>
> That means masked_user_read_access_begin() is used when user memory is
> exclusively read during the window, masked_user_write_access_begin()
> is used when user memory is exclusively writen during the window,
> masked_user_access_begin() remains and is used when both reads and
> writes are performed during the open window. Each of them is expected
> to be terminated by the matching user_read_access_end(),
> user_write_access_end() and user_access_end().
>
> Have them default to masked_user_access_begin() when they are
> not defined.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Can we please coordinate on that vs. the scoped_access() work as this
nicely collides all over the place?
Thanks,
tglx
Le 22/10/2025 à 19:05, Thomas Gleixner a écrit : > On Fri, Oct 17 2025 at 12:20, Christophe Leroy wrote: >> Allthough masked_user_access_begin() is to only be used when reading >> data from user at the moment, introduce masked_user_read_access_begin() >> and masked_user_write_access_begin() in order to match >> user_read_access_begin() and user_write_access_begin(). >> >> That means masked_user_read_access_begin() is used when user memory is >> exclusively read during the window, masked_user_write_access_begin() >> is used when user memory is exclusively writen during the window, >> masked_user_access_begin() remains and is used when both reads and >> writes are performed during the open window. Each of them is expected >> to be terminated by the matching user_read_access_end(), >> user_write_access_end() and user_access_end(). >> >> Have them default to masked_user_access_begin() when they are >> not defined. >> >> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> > > Can we please coordinate on that vs. the scoped_access() work as this > nicely collides all over the place? Sure, I will rebase on top of your series. Once it is rebased, could you take the non powerpc patches in your tree ? Thanks Christophe
On Tue, Nov 04 2025 at 07:39, Christophe Leroy wrote:
> Le 22/10/2025 à 19:05, Thomas Gleixner a écrit :
>> On Fri, Oct 17 2025 at 12:20, Christophe Leroy wrote:
>>> Allthough masked_user_access_begin() is to only be used when reading
>>> data from user at the moment, introduce masked_user_read_access_begin()
>>> and masked_user_write_access_begin() in order to match
>>> user_read_access_begin() and user_write_access_begin().
>>>
>>> That means masked_user_read_access_begin() is used when user memory is
>>> exclusively read during the window, masked_user_write_access_begin()
>>> is used when user memory is exclusively writen during the window,
>>> masked_user_access_begin() remains and is used when both reads and
>>> writes are performed during the open window. Each of them is expected
>>> to be terminated by the matching user_read_access_end(),
>>> user_write_access_end() and user_access_end().
>>>
>>> Have them default to masked_user_access_begin() when they are
>>> not defined.
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>>
>> Can we please coordinate on that vs. the scoped_access() work as this
>> nicely collides all over the place?
>
> Sure, I will rebase on top of your series.
>
> Once it is rebased, could you take the non powerpc patches in your tree ?
Sure. The current lot is at:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git scoped-uaccess
Thanks,
tglx
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