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Date: Mon, 29 Jun 2015 16:13:16 -0700
From: Greg KH <gregkh@linuxfoundation.org>
To: Sheng Yong <shengyong1@huawei.com>
Cc: stable@vger.kernel.org, oleg@redhat.com, mgrondona@llnl.gov
Subject: Re: [request for inclusion 3.10][PATCH 0/2] fix thread cannot access
 stat in the same group
Message-ID: <20150629231316.GA29763@kroah.com>
References: <1431914844-66627-1-git-send-email-shengyong1@huawei.com>
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On Mon, May 18, 2015 at 02:07:22AM +0000, Sheng Yong wrote:
> Hi, Greg,
> 
> In the case that threads in the same group try to access one of their
> /proc/$PID/{stat,exe,etc.}, the thread only gets 0 at some fields, like
> eip. This is because that these interfaces only allows the same task to
> get these data. But one thread should not deny the access from another
> thread in `the same group.
> 
> The testcase is:
> =====================
> #include <sys/types.h>
> #include <pthread.h>
> #include <stdio.h>
> #include <unistd.h>
> #include <asm/unistd.h>
> #include <fcntl.h>
> #include <string.h>
> #include <sys/stat.h>
> 
> pid_t tid = 0;
> 
> void print_stat_eip(pid_t child)
> {
>         int fd, i;
>         char buf[4096], *str, *part;
> 
>         sprintf(buf, "/proc/%d/stat", child);
> 
>         fd = open(buf, O_RDONLY);
>         read(fd, buf, 4096);
>         close(fd);
>         buf[4095] = '\0';
> 
>         str = buf;
> 
>         part = strtok(str, " ");
>         i = 0;
>         while (part) {
>                 i++;
>                 if (i == 30) { // eip
>                         printf("eip: %s\n", part);
>                         break;  
>                 }
>                 part = strtok(NULL, " ");
>         }    
> }
> 
> void *child_func(void *arg)
> {   
>         tid = syscall(__NR_gettid);
>         while(1)
>                 sleep(10000);
>         return NULL;
> }   
> 
> int main(int argc, char **argv)
> {
>         pthread_t child;
> 
>         setuid(1000); // 1000 is the uid of a non-root user
>         pthread_create(&child, NULL, child_func, NULL);
>         sleep(1);
>         print_stat_eip(tid);
> }
> =====================
> 
> The following two patches fix this.
> 
> thanks,
> Sheng
> 
> Mark Grondona (1):
>   __ptrace_may_access() should not deny sub-threads
> 
> Oleg Nesterov (1):
>   include/linux/sched.h: don't use task->pid/tgid in
>     same_thread_group/has_group_leader_pid
> 
>  include/linux/sched.h | 8 ++++----
>  kernel/ptrace.c       | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> -- 
> 1.8.3.4

Thanks, both now applied.

greg k-h