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From: Oleg Nesterov <oleg@redhat.com>
To: Gregory Price <gregory.price@memverge.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Gregory Price <gourry.memverge@gmail.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Linux-Arch <linux-arch@vger.kernel.org>,
	avagin@gmail.com, Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	krisman@collabora.com, Thomas Gleixner <tglx@linutronix.de>,
	Jonathan Corbet <corbet@lwn.net>, shuah <shuah@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	tongtiangen@huawei.com, Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok
Date: Wed, 29 Mar 2023 19:13:22 +0200	[thread overview]
Message-ID: <20230329171322.GB4477@redhat.com> (raw)
In-Reply-To: <ZCO20bzX/IB8J6Gp@memverge.com>

On 03/28, Gregory Price wrote:
>
> Not sure how I should proceed here,

Can't we just kill this access_ok() in set_syscall_user_dispatch() ?
I don't think it buys too much.

Oleg.

diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
index 0b6379adff6b..d2e516ece52b 100644
--- a/kernel/entry/syscall_user_dispatch.c
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -43,11 +43,7 @@ bool syscall_user_dispatch(struct pt_regs *regs)
 		return false;
 
 	if (likely(sd->selector)) {
-		/*
-		 * access_ok() is performed once, at prctl time, when
-		 * the selector is loaded by userspace.
-		 */
-		if (unlikely(__get_user(state, sd->selector))) {
+		if (unlikely(get_user(state, sd->selector))) {
 			force_exit_sig(SIGSEGV);
 			return true;
 		}
@@ -86,9 +82,6 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
 		if (offset && offset + len <= offset)
 			return -EINVAL;
 
-		if (selector && !access_ok(selector, sizeof(*selector)))
-			return -EFAULT;
-
 		break;
 	default:
 		return -EINVAL;


WARNING: multiple messages have this Message-ID (diff)
From: Oleg Nesterov <oleg@redhat.com>
To: Gregory Price <gregory.price@memverge.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Gregory Price <gourry.memverge@gmail.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Linux-Arch <linux-arch@vger.kernel.org>,
	avagin@gmail.com, Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	krisman@collabora.com, Thomas Gleixner <tglx@linutronix.de>,
	Jonathan Corbet <corbet@lwn.net>, shuah <shuah@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	tongtiangen@huawei.com, Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok
Date: Wed, 29 Mar 2023 19:13:22 +0200	[thread overview]
Message-ID: <20230329171322.GB4477@redhat.com> (raw)
In-Reply-To: <ZCO20bzX/IB8J6Gp@memverge.com>

On 03/28, Gregory Price wrote:
>
> Not sure how I should proceed here,

Can't we just kill this access_ok() in set_syscall_user_dispatch() ?
I don't think it buys too much.

Oleg.

diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
index 0b6379adff6b..d2e516ece52b 100644
--- a/kernel/entry/syscall_user_dispatch.c
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -43,11 +43,7 @@ bool syscall_user_dispatch(struct pt_regs *regs)
 		return false;
 
 	if (likely(sd->selector)) {
-		/*
-		 * access_ok() is performed once, at prctl time, when
-		 * the selector is loaded by userspace.
-		 */
-		if (unlikely(__get_user(state, sd->selector))) {
+		if (unlikely(get_user(state, sd->selector))) {
 			force_exit_sig(SIGSEGV);
 			return true;
 		}
@@ -86,9 +82,6 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
 		if (offset && offset + len <= offset)
 			return -EINVAL;
 
-		if (selector && !access_ok(selector, sizeof(*selector)))
-			return -EFAULT;
-
 		break;
 	default:
 		return -EINVAL;


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  reply	other threads:[~2023-03-29 17:14 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-28 16:48 [PATCH v14 0/4] Checkpoint Support for Syscall User Dispatch Gregory Price
2023-03-28 16:48 ` Gregory Price
2023-03-28 16:48 ` [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok Gregory Price
2023-03-28 16:48   ` Gregory Price
2023-03-28 18:46   ` Arnd Bergmann
2023-03-28 18:46     ` Arnd Bergmann
2023-03-29 15:15   ` Oleg Nesterov
2023-03-29 15:15     ` Oleg Nesterov
2023-03-29 15:41     ` Arnd Bergmann
2023-03-29 15:41       ` Arnd Bergmann
2023-03-29 16:03       ` Oleg Nesterov
2023-03-29 16:03         ` Oleg Nesterov
2023-03-29  3:56         ` Gregory Price
2023-03-29  3:56           ` Gregory Price
2023-03-29 17:13           ` Oleg Nesterov [this message]
2023-03-29 17:13             ` Oleg Nesterov
2023-03-29  5:37             ` Gregory Price
2023-03-29  5:37               ` Gregory Price
2023-03-29 17:58               ` Oleg Nesterov
2023-03-29 17:58                 ` Oleg Nesterov
2023-03-29  5:54                 ` Gregory Price
2023-03-29  5:54                   ` Gregory Price
2023-03-29 18:13                   ` Oleg Nesterov
2023-03-29 18:13                     ` Oleg Nesterov
2023-03-29 10:02                 ` Gregory Price
2023-03-29 10:02                   ` Gregory Price
2023-03-29 23:54                   ` Oleg Nesterov
2023-03-29 23:54                     ` Oleg Nesterov
2023-03-29 18:29         ` Arnd Bergmann
2023-03-29 18:29           ` Arnd Bergmann
2023-03-29 16:22   ` Catalin Marinas
2023-03-29 16:22     ` Catalin Marinas
2023-03-29  4:34     ` Gregory Price
2023-03-29  4:34       ` Gregory Price
2023-03-30 14:05       ` Catalin Marinas
2023-03-30 14:05         ` Catalin Marinas
2023-03-30  4:18         ` Gregory Price
2023-03-30  4:18           ` Gregory Price
2023-03-28 16:48 ` [PATCH v14 2/4] syscall_user_dispatch: helper function to operate on given task Gregory Price
2023-03-28 16:48   ` Gregory Price
2023-03-28 16:48 ` [PATCH v14 3/4] ptrace,syscall_user_dispatch: checkpoint/restore support for SUD Gregory Price
2023-03-28 16:48   ` Gregory Price
2023-03-28 16:48 ` [PATCH v14 4/4] selftest,ptrace: Add selftest for syscall user dispatch config api Gregory Price
2023-03-28 16:48   ` Gregory Price

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