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fork: fold legacy_clone_args_valid() into _do_fork() 

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>
This commit is contained in:
Christian Brauner 2020-06-08 17:28:50 +02:00
parent 48778464bb
commit 3af8588c77
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
4 changed files with 14 additions and 23 deletions
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3
arch/m68k/kernel/process.c
View File

@ -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);
}

3
arch/x86/kernel/sys_ia32.c
View File

@ -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 */

1
include/linux/sched/task.h
View File

@ -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);

30
kernel/fork.c
View File

@ -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