clone: fix CLONE_PIDFD support

The introduction of clone3 syscall accidentally broke CLONE_PIDFD support in traditional clone syscall on compat x86 and those architectures that use do_fork to implement clone syscall. This bug was found by strace test suite.

Dmitry V. Levin committed 7 years ago

Commit 028b6e81 parent 964a4ea3 files · +20 −2Browse files

Unified · Split

3 files

arch/x86/ia32/sys_ia32.c +4 −0
include/linux/sched/task.h +1 −0
kernel/fork.c +15 −2

arch/x86/ia32/sys_ia32.c+4−0

@@ -239,6 +239,7 @@ COMPAT_SYSCALL_DEFINE5(x86_clone, unsigned long, clone_flags, · 238 unmodified lines
239	239	{
240	240	struct kernel_clone_args args = {
241	241	.flags = (clone_flags & ~CSIGNAL),
	242	+ .pidfd = parent_tidptr,
242	243	.child_tid = child_tidptr,
243	244	.parent_tid = parent_tidptr,
244	245	.exit_signal = (clone_flags & CSIGNAL),
@@ -246,5 +247,8 @@ COMPAT_SYSCALL_DEFINE5(x86_clone, unsigned long, clone_flags, · 1 unmodified line
246	247	.tls = tls_val,
247	248	};
248	249
	250	+ if (!legacy_clone_args_valid(&args))
	251	+ return -EINVAL;
	252	+
249	253	return _do_fork(&args);
250	254	}

include/linux/sched/task.h+1−0

@@ -89,6 +89,7 @@ extern void exit_files(struct task_struct *); · 88 unmodified lines
89	89	extern void exit_itimers(struct signal_struct *);
90	90
91	91	extern long _do_fork(struct kernel_clone_args *kargs);
	92	+extern bool legacy_clone_args_valid(const struct kernel_clone_args *kargs);
92	93	extern long do_fork(unsigned long, unsigned long, unsigned long, int __user , int __user );
93	94	struct task_struct *fork_idle(int);
94	95	struct mm_struct *copy_init_mm(void);

kernel/fork.c+15−2

@@ -2406,6 +2406,16 @@ long _do_fork(struct kernel_clone_args *args) · 2405 unmodified lines
2406	2406	return nr;
2407	2407	}
2408	2408
	2409	+bool legacy_clone_args_valid(const struct kernel_clone_args *kargs)
	2410	+{
	2411	+ /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
	2412	+ if ((kargs->flags & CLONE_PIDFD) &&
	2413	+ (kargs->flags & CLONE_PARENT_SETTID))
	2414	+ return false;
	2415	+
	2416	+ return true;
	2417	+}
	2418	+
2409	2419	#ifndef CONFIG_HAVE_COPY_THREAD_TLS
2410	2420	/* For compatibility with architectures that call do_fork directly rather than
2411	2421	* using the syscall entry points below. */
@@ -2417,6 +2427,7 @@ long do_fork(unsigned long clone_flags, · 5 unmodified lines
2417	2427	{
2418	2428	struct kernel_clone_args args = {
2419	2429	.flags = (clone_flags & ~CSIGNAL),
	2430	+ .pidfd = parent_tidptr,
2420	2431	.child_tid = child_tidptr,
2421	2432	.parent_tid = parent_tidptr,
2422	2433	.exit_signal = (clone_flags & CSIGNAL),
@@ -2424,6 +2435,9 @@ long do_fork(unsigned long clone_flags, · 1 unmodified line
2424	2435	.stack_size = stack_size,
2425	2436	};
2426	2437
	2438	+ if (!legacy_clone_args_valid(&args))
	2439	+ return -EINVAL;
	2440	+
2427	2441	return _do_fork(&args);
2428	2442	}
2429	2443	#endif
@@ -2505,8 +2519,7 @@ SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp, · 75 unmodified lines
2505	2519	.tls = tls,
2506	2520	};
2507	2521
2508		− /* clone(CLONE_PIDFD) uses parent_tidptr to return a pidfd */
2509		− if ((clone_flags & CLONE_PIDFD) && (clone_flags & CLONE_PARENT_SETTID))
	2522	+ if (!legacy_clone_args_valid(&args))
2510	2523	return -EINVAL;
2511	2524
2512	2525	return _do_fork(&args);

clone: fix CLONE_PIDFD support

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