perf: Introduce a flag to enable close-on-exec in perf_event_open()
Unlike recent modern userspace API such as: epoll_create1 (EPOLL_CLOEXEC), eventfd (EFD_CLOEXEC), fanotify_init (FAN_CLOEXEC), inotify_init1 (IN_CLOEXEC), signalfd (SFD_CLOEXEC), timerfd_create (TFD_CLOEXEC), or the venerable general purpose open (O_CLOEXEC), perf_event_open() syscall lack a flag to atomically set FD_CLOEXEC (eg. close-on-exec) flag on file descriptor it returns to userspace. The present patch adds a PERF_FLAG_FD_CLOEXEC flag to allow perf_event_open() syscall to atomically set close-on-exec. Having this flag will enable userspace to remove the file descriptor from the list of file descriptors being inherited across exec, without the need to call fcntl(fd, F_SETFD, FD_CLOEXEC) and the associated race condition between the current thread and another thread calling fork(2) then execve(2). Links: - Secure File Descriptor Handling (Ulrich Drepper, 2008) http://udrepper.livejournal.com/20407.html - Excuse me son, but your code is leaking !!! (Dan Walsh, March 2012) http://danwalsh.livejournal.com/53603.html - Notes in DMA buffer sharing: leak and security hole http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/dma-buf-sharing.txt?id=v3.13-rc3#n428 Signed-off-by: Yann Droneaud <ydroneaud@opteya.com> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/8c03f54e1598b1727c19706f3af03f98685d9fe6.1388952061.git.ydroneaud@opteya.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -724,6 +724,7 @@ enum perf_callchain_context {
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#define PERF_FLAG_FD_NO_GROUP (1U << 0)
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#define PERF_FLAG_FD_OUTPUT (1U << 1)
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#define PERF_FLAG_PID_CGROUP (1U << 2) /* pid=cgroup id, per-cpu mode only */
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#define PERF_FLAG_FD_CLOEXEC (1U << 3) /* O_CLOEXEC */
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union perf_mem_data_src {
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__u64 val;
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@ -119,7 +119,8 @@ static int cpu_function_call(int cpu, int (*func) (void *info), void *info)
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#define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\
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PERF_FLAG_FD_OUTPUT |\
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PERF_FLAG_PID_CGROUP)
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PERF_FLAG_PID_CGROUP |\
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PERF_FLAG_FD_CLOEXEC)
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/*
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* branch priv levels that need permission checks
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@ -6982,6 +6983,7 @@ SYSCALL_DEFINE5(perf_event_open,
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int event_fd;
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int move_group = 0;
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int err;
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int f_flags = O_RDWR;
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/* for future expandability... */
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if (flags & ~PERF_FLAG_ALL)
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@ -7010,7 +7012,10 @@ SYSCALL_DEFINE5(perf_event_open,
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if ((flags & PERF_FLAG_PID_CGROUP) && (pid == -1 || cpu == -1))
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return -EINVAL;
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event_fd = get_unused_fd();
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if (flags & PERF_FLAG_FD_CLOEXEC)
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f_flags |= O_CLOEXEC;
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event_fd = get_unused_fd_flags(f_flags);
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if (event_fd < 0)
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return event_fd;
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@ -7132,7 +7137,8 @@ SYSCALL_DEFINE5(perf_event_open,
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goto err_context;
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}
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event_file = anon_inode_getfile("[perf_event]", &perf_fops, event, O_RDWR);
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event_file = anon_inode_getfile("[perf_event]", &perf_fops, event,
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f_flags);
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if (IS_ERR(event_file)) {
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err = PTR_ERR(event_file);
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goto err_context;
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