Allthough masked_user_access_begin() seems 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().
Have them default to masked_user_access_begin() when they are
not defined.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
fs/select.c | 2 +-
include/linux/uaccess.h | 8 ++++++++
kernel/futex/futex.h | 4 ++--
lib/strncpy_from_user.c | 2 +-
lib/strnlen_user.c | 2 +-
5 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/fs/select.c b/fs/select.c
index 9fb650d03d52..d8547bedf5eb 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 7c06f4795670..682a0cd2fe51 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -41,6 +41,14 @@
#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 fcd1617212ee..6cfcafa00736 100644
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -305,7 +305,7 @@ 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);
@@ -320,7 +320,7 @@ 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_read_access_begin(to);
else if (!user_read_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 6dc234913dd5..5bb752ff7c61 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 6e489f9e90f1..4a6574b67f82 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;
--
2.49.0On Sun, 22 Jun 2025 11:52:39 +0200
Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
> Allthough masked_user_access_begin() seems 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().
>
> Have them default to masked_user_access_begin() when they are
> not defined.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> fs/select.c | 2 +-
> include/linux/uaccess.h | 8 ++++++++
> kernel/futex/futex.h | 4 ++--
> lib/strncpy_from_user.c | 2 +-
> lib/strnlen_user.c | 2 +-
> 5 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/fs/select.c b/fs/select.c
> index 9fb650d03d52..d8547bedf5eb 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 7c06f4795670..682a0cd2fe51 100644
> --- a/include/linux/uaccess.h
> +++ b/include/linux/uaccess.h
> @@ -41,6 +41,14 @@
> #ifdef masked_user_access_begin
> #define can_do_masked_user_access() 1
> #else
> #define can_do_masked_user_access() 0
> #define masked_user_access_begin(src) NULL
> #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
I think that needs merging with the bit above.
Perhaps generating something like:
#ifdef masked_user_access_begin
#define masked_user_read_access_begin masked_user_access_begin
#define masked_user_write_access_begin masked_user_access_begin
#endif
#ifdef masked_user_read_access_begin
#define can_do_masked_user_access() 1
#else
#define can_do_masked_user_access() 0
#define masked_user_read_access_begin(src) NULL
#define masked_user_write_access_begin(src) NULL
#define mask_user_address(src) (src)
#endif
Otherwise you'll have to #define masked_user_access_begin even though
it is never used.
Two more patches could change x86-64 to define both and then remove
the 'then unused' first check - but that has to be for later.
David
Le 22/06/2025 à 18:35, David Laight a écrit :
> On Sun, 22 Jun 2025 11:52:39 +0200
> Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
>
>> Allthough masked_user_access_begin() seems 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().
>>
>> Have them default to masked_user_access_begin() when they are
>> not defined.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>> fs/select.c | 2 +-
>> include/linux/uaccess.h | 8 ++++++++
>> kernel/futex/futex.h | 4 ++--
>> lib/strncpy_from_user.c | 2 +-
>> lib/strnlen_user.c | 2 +-
>> 5 files changed, 13 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/select.c b/fs/select.c
>> index 9fb650d03d52..d8547bedf5eb 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 7c06f4795670..682a0cd2fe51 100644
>> --- a/include/linux/uaccess.h
>> +++ b/include/linux/uaccess.h
>> @@ -41,6 +41,14 @@
>
>> #ifdef masked_user_access_begin
>> #define can_do_masked_user_access() 1
>> #else
>> #define can_do_masked_user_access() 0
>> #define masked_user_access_begin(src) NULL
>> #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
>
> I think that needs merging with the bit above.
> Perhaps generating something like:
>
> #ifdef masked_user_access_begin
> #define masked_user_read_access_begin masked_user_access_begin
> #define masked_user_write_access_begin masked_user_access_begin
> #endif
>
> #ifdef masked_user_read_access_begin
> #define can_do_masked_user_access() 1
> #else
> #define can_do_masked_user_access() 0
> #define masked_user_read_access_begin(src) NULL
> #define masked_user_write_access_begin(src) NULL
> #define mask_user_address(src) (src)
> #endif
>
> Otherwise you'll have to #define masked_user_access_begin even though
> it is never used.
I'm not sure I understand what you mean.
masked_user_access_begin() is used, for instance in
arch/x86/include/asm/futex.h so it will remain.
masked_user_access_begin() is the analogy of user_access_begin(), it
starts a read-write user access and is worth it.
>
> Two more patches could change x86-64 to define both and then remove
> the 'then unused' first check - but that has to be for later.
>
Christophe
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