From: Christian Brauner <christian.brauner@ubuntu.com>
To: linux-kernel@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Christian Brauner <christian.brauner@ubuntu.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
Geert Uytterhoeven <geert@linux-m68k.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
linux-m68k@lists.linux-m68k.org, x86@kernel.org
Subject: [PATCH 01/17] fork: fold legacy_clone_args_valid() into _do_fork()
Date: Tue, 23 Jun 2020 01:43:10 +0200 [thread overview]
Message-ID: <20200622234326.906346-2-christian.brauner@ubuntu.com> (raw)
In-Reply-To: <20200622234326.906346-1-christian.brauner@ubuntu.com>
This separate helper only existed to guarantee the mutual exclusivity of
CLONE_PIDFD and CLONE_PARENT_SETTID for legacy clone since CLONE_PIDFD
abuses the parent_tid field to return the pidfd. But we can actually handle
this uniformely thus removing the helper. For legacy clone we can detect
that CLONE_PIDFD is specified in conjunction with CLONE_PARENT_SETTID
because they will share the same memory which is invalid and for clone3()
setting the separate pidfd and parent_tid fields to the same memory is
bogus as well. So fold that helper directly into _do_fork() by detecting
this case.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: linux-m68k@lists.linux-m68k.org
Cc: x86@kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
arch/m68k/kernel/process.c | 3 ---
arch/x86/kernel/sys_ia32.c | 3 ---
include/linux/sched/task.h | 1 -
kernel/fork.c | 30 ++++++++++++++----------------
4 files changed, 14 insertions(+), 23 deletions(-)
diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c
index 90ae376b7ab1..0608439ba452 100644
--- a/arch/m68k/kernel/process.c
+++ b/arch/m68k/kernel/process.c
@@ -125,9 +125,6 @@ asmlinkage int m68k_clone(struct pt_regs *regs)
.tls = regs->d5,
};
- if (!legacy_clone_args_valid(&args))
- return -EINVAL;
-
return _do_fork(&args);
}
diff --git a/arch/x86/kernel/sys_ia32.c b/arch/x86/kernel/sys_ia32.c
index f8d65c99feb8..720cde885042 100644
--- a/arch/x86/kernel/sys_ia32.c
+++ b/arch/x86/kernel/sys_ia32.c
@@ -251,9 +251,6 @@ COMPAT_SYSCALL_DEFINE5(ia32_clone, unsigned long, clone_flags,
.tls = tls_val,
};
- if (!legacy_clone_args_valid(&args))
- return -EINVAL;
-
return _do_fork(&args);
}
#endif /* CONFIG_IA32_EMULATION */
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 38359071236a..ddce0ea515d1 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -96,7 +96,6 @@ extern void exit_files(struct task_struct *);
extern void exit_itimers(struct signal_struct *);
extern long _do_fork(struct kernel_clone_args *kargs);
-extern bool legacy_clone_args_valid(const struct kernel_clone_args *kargs);
extern long do_fork(unsigned long, unsigned long, unsigned long, int __user *, int __user *);
struct task_struct *fork_idle(int);
struct mm_struct *copy_init_mm(void);
diff --git a/kernel/fork.c b/kernel/fork.c
index 142b23645d82..9875aeb2ba41 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2422,6 +2422,20 @@ long _do_fork(struct kernel_clone_args *args)
int trace = 0;
long nr;
+ /*
+ * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
+ * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
+ * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
+ * field in struct clone_args and it still doesn't make sense to have
+ * them both point at the same memory location. Performing this check
+ * here has the advantage that we don't need to have a separate helper
+ * to check for legacy clone().
+ */
+ if ((args->flags & CLONE_PIDFD) &&
+ (args->flags & CLONE_PARENT_SETTID) &&
+ (args->pidfd == args->parent_tid))
+ return -EINVAL;
+
/*
* Determine whether and which event to report to ptracer. When
* called from kernel_thread or CLONE_UNTRACED is explicitly
@@ -2479,16 +2493,6 @@ long _do_fork(struct kernel_clone_args *args)
return nr;
}
-bool legacy_clone_args_valid(const struct kernel_clone_args *kargs)
-{
- /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
- if ((kargs->flags & CLONE_PIDFD) &&
- (kargs->flags & CLONE_PARENT_SETTID))
- return false;
-
- return true;
-}
-
#ifndef CONFIG_HAVE_COPY_THREAD_TLS
/* For compatibility with architectures that call do_fork directly rather than
* using the syscall entry points below. */
@@ -2508,9 +2512,6 @@ long do_fork(unsigned long clone_flags,
.stack_size = stack_size,
};
- if (!legacy_clone_args_valid(&args))
- return -EINVAL;
-
return _do_fork(&args);
}
#endif
@@ -2593,9 +2594,6 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
.tls = tls,
};
- if (!legacy_clone_args_valid(&args))
- return -EINVAL;
-
return _do_fork(&args);
}
#endif
--
2.27.0
next prev parent reply other threads:[~2020-06-22 23:47 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-22 23:43 [PATCH 00/17] arch: remove do_fork() and HAVE_COPY_THREAD_TLS Christian Brauner
2020-06-22 23:43 ` Christian Brauner [this message]
[not found] ` <20200627082748.GM5535@shao2-debian>
2020-06-27 12:23 ` [fork] 11689456e6: ltp.clone302.fail Christian Brauner
2020-06-22 23:43 ` [PATCH 02/17] sparc64: enable HAVE_COPY_THREAD_TLS Christian Brauner
2020-06-23 3:35 ` David Miller
2020-06-23 8:42 ` Christian Brauner
2020-06-22 23:43 ` [PATCH 03/17] sparc: share process creation helpers between sparc and sparc64 Christian Brauner
2020-06-22 23:43 ` [PATCH 04/17] sparc: unconditionally enable HAVE_COPY_THREAD_TLS Christian Brauner
2020-06-22 23:43 ` [PATCH 05/17] ia64: enable HAVE_COPY_THREAD_TLS, switch to kernel_clone_args Christian Brauner
2020-06-22 23:43 ` [PATCH 06/17] nios2: " Christian Brauner
2020-06-22 23:43 ` [PATCH 07/17] h8300: select " Christian Brauner
2020-06-22 23:43 ` [PATCH 08/17] fork: remove do_fork() Christian Brauner
2020-06-22 23:43 ` [PATCH 09/17] alpha: switch to copy_thread_tls() Christian Brauner
2020-06-22 23:43 ` [PATCH 10/17] c6x: " Christian Brauner
2020-06-22 23:43 ` [PATCH 11/17] hexagon: " Christian Brauner
2020-06-23 16:11 ` Brian Cain
2020-06-22 23:43 ` [PATCH 12/17] microblaze: " Christian Brauner
2020-06-22 23:43 ` [PATCH 13/17] nds32: " Christian Brauner
2020-06-22 23:43 ` [PATCH 14/17] sh: " Christian Brauner
2020-06-22 23:43 ` [PATCH 15/17] unicore: " Christian Brauner
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