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Message-ID: <a4ef0a8e1659805c60fafc8d3b073ecd08117241.1760529207.git.christophe.leroy@csgroup.eu>
Date: Fri, 17 Oct 2025 12:20:59 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>,
Jan Kara <jack@...e.cz>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Darren Hart <dvhart@...radead.org>,
Davidlohr Bueso <dave@...olabs.net>,
"Andre Almeida" <andrealmeid@...lia.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Eric Dumazet <edumazet@...gle.com>,
Kuniyuki Iwashima <kuniyu@...gle.com>,
Paolo Abeni <pabeni@...hat.com>,
Willem de Bruijn <willemb@...gle.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Simon Horman <horms@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Madhavan Srinivasan <maddy@...ux.ibm.com>,
Michael Ellerman <mpe@...erman.id.au>,
Nicholas Piggin <npiggin@...il.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
linux-block@...r.kernel.org,
linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org,
netdev@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v3 03/10] uaccess: Add masked_user_{read/write}_access_begin
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@...roup.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;
--
2.49.0
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