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[patch V6 05/31] rseq: Simplify registration

Thomas Gleixner posted 31 patches 1 month, 3 weeks ago
[patch V6 05/31] rseq: Simplify registration
Posted by Thomas Gleixner 1 month, 3 weeks ago 
There is no point to read the critical section element in the newly
registered user space RSEQ struct first in order to clear it.

Just clear it and be done with it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

---
 kernel/rseq.c |   10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -492,11 +492,9 @@ void rseq_syscall(struct pt_regs *regs)
 /*
  * sys_rseq - setup restartable sequences for caller thread.
  */
-SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
-		int, flags, u32, sig)
+SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int, flags, u32, sig)
 {
 	int ret;
-	u64 rseq_cs;
 
 	if (flags & RSEQ_FLAG_UNREGISTER) {
 		if (flags & ~RSEQ_FLAG_UNREGISTER)
@@ -557,11 +555,9 @@ SYSCALL_DEFINE4(rseq, struct rseq __user
 	 * avoid a potential segfault on return to user-space. The proper thing
 	 * to do would have been to fail the registration but this would break
 	 * older libcs that reuse the rseq area for new threads without
-	 * clearing the fields.
+	 * clearing the fields. Don't bother reading it, just reset it.
 	 */
-	if (rseq_get_rseq_cs_ptr_val(rseq, &rseq_cs))
-	        return -EFAULT;
-	if (rseq_cs && clear_rseq_cs(rseq))
+	if (put_user(0UL, &rseq->rseq_cs))
 		return -EFAULT;
 
 #ifdef CONFIG_DEBUG_RSEQ
[tip: core/rseq] rseq: Simplify registration
Posted by tip-bot2 for Thomas Gleixner 1 month, 1 week ago 
The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     067b3b41b4dd5bf51d6874206f5c1f72e0684eeb
Gitweb:        https://git.kernel.org/tip/067b3b41b4dd5bf51d6874206f5c1f72e0684eeb
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:44:24 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 04 Nov 2025 08:30:05 +01:00

rseq: Simplify registration

There is no point to read the critical section element in the newly
registered user space RSEQ struct first in order to clear it.

Just clear it and be done with it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251027084306.274661227@linutronix.de
---
 kernel/rseq.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/kernel/rseq.c b/kernel/rseq.c
index 51fafc4..80af48a 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -492,11 +492,9 @@ void rseq_syscall(struct pt_regs *regs)
 /*
  * sys_rseq - setup restartable sequences for caller thread.
  */
-SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
-		int, flags, u32, sig)
+SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int, flags, u32, sig)
 {
 	int ret;
-	u64 rseq_cs;
 
 	if (flags & RSEQ_FLAG_UNREGISTER) {
 		if (flags & ~RSEQ_FLAG_UNREGISTER)
@@ -557,11 +555,9 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
 	 * avoid a potential segfault on return to user-space. The proper thing
 	 * to do would have been to fail the registration but this would break
 	 * older libcs that reuse the rseq area for new threads without
-	 * clearing the fields.
+	 * clearing the fields. Don't bother reading it, just reset it.
 	 */
-	if (rseq_get_rseq_cs_ptr_val(rseq, &rseq_cs))
-	        return -EFAULT;
-	if (rseq_cs && clear_rseq_cs(rseq))
+	if (put_user(0UL, &rseq->rseq_cs))
 		return -EFAULT;
 
 #ifdef CONFIG_DEBUG_RSEQ
[tip: core/rseq] rseq: Simplify registration
Posted by tip-bot2 for Thomas Gleixner 1 month, 2 weeks ago 
The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     ae3051d908dda0409d18d8e31a3b89023376ada3
Gitweb:        https://git.kernel.org/tip/ae3051d908dda0409d18d8e31a3b89023376ada3
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:44:24 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 03 Nov 2025 15:26:13 +01:00

rseq: Simplify registration

There is no point to read the critical section element in the newly
registered user space RSEQ struct first in order to clear it.

Just clear it and be done with it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251027084306.274661227@linutronix.de
---
 kernel/rseq.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/kernel/rseq.c b/kernel/rseq.c
index 51fafc4..80af48a 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -492,11 +492,9 @@ void rseq_syscall(struct pt_regs *regs)
 /*
  * sys_rseq - setup restartable sequences for caller thread.
  */
-SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
-		int, flags, u32, sig)
+SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int, flags, u32, sig)
 {
 	int ret;
-	u64 rseq_cs;
 
 	if (flags & RSEQ_FLAG_UNREGISTER) {
 		if (flags & ~RSEQ_FLAG_UNREGISTER)
@@ -557,11 +555,9 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
 	 * avoid a potential segfault on return to user-space. The proper thing
 	 * to do would have been to fail the registration but this would break
 	 * older libcs that reuse the rseq area for new threads without
-	 * clearing the fields.
+	 * clearing the fields. Don't bother reading it, just reset it.
 	 */
-	if (rseq_get_rseq_cs_ptr_val(rseq, &rseq_cs))
-	        return -EFAULT;
-	if (rseq_cs && clear_rseq_cs(rseq))
+	if (put_user(0UL, &rseq->rseq_cs))
 		return -EFAULT;
 
 #ifdef CONFIG_DEBUG_RSEQ
[tip: core/rseq] rseq: Simplify registration
Posted by tip-bot2 for Thomas Gleixner 1 month, 2 weeks ago 
The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     bd88944825d9579d1240dcc55b5f57635298a121
Gitweb:        https://git.kernel.org/tip/bd88944825d9579d1240dcc55b5f57635298a121
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:44:24 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 29 Oct 2025 11:07:12 +01:00

rseq: Simplify registration

There is no point to read the critical section element in the newly
registered user space RSEQ struct first in order to clear it.

Just clear it and be done with it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251027084306.274661227@linutronix.de
---
 kernel/rseq.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/kernel/rseq.c b/kernel/rseq.c
index 51fafc4..80af48a 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -492,11 +492,9 @@ void rseq_syscall(struct pt_regs *regs)
 /*
  * sys_rseq - setup restartable sequences for caller thread.
  */
-SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
-		int, flags, u32, sig)
+SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int, flags, u32, sig)
 {
 	int ret;
-	u64 rseq_cs;
 
 	if (flags & RSEQ_FLAG_UNREGISTER) {
 		if (flags & ~RSEQ_FLAG_UNREGISTER)
@@ -557,11 +555,9 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
 	 * avoid a potential segfault on return to user-space. The proper thing
 	 * to do would have been to fail the registration but this would break
 	 * older libcs that reuse the rseq area for new threads without
-	 * clearing the fields.
+	 * clearing the fields. Don't bother reading it, just reset it.
 	 */
-	if (rseq_get_rseq_cs_ptr_val(rseq, &rseq_cs))
-	        return -EFAULT;
-	if (rseq_cs && clear_rseq_cs(rseq))
+	if (put_user(0UL, &rseq->rseq_cs))
 		return -EFAULT;
 
 #ifdef CONFIG_DEBUG_RSEQ

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