On Precise 3.13 $ cat /proc/self/stack cat: /proc/self/stack: Permission denied $ sudo cat /proc/self/stack [<ffffffff810730b0>] do_wait+0x1f0/0x280 [<ffffffff8107403f>] SyS_wait4+0xaf/0x120 [<ffffffff817823fc>] system_call_fastpath+0x26/0x2b [<ffffffffffffffff>] 0xffffffffffffffff $ ls -l /proc/self/stack -r--r--r-- 1 ubuntu ubuntu 0 Jan 24 04:06 /proc/self/stack
But on Bionic, the file permission is: $ ls -l /proc/self/stack -r-------- 1 ubuntu ubuntu 0 Jan 24 12:07 /proc/self/stack
On Precise 3.13 0b0>] do_wait+0x1f0/0x280 03f>] SyS_wait4+ 0xaf/0x120 3fc>] system_ call_fastpath+ 0x26/0x2b fff>] 0xffffffffffffffff
$ cat /proc/self/stack
cat: /proc/self/stack: Permission denied
$ sudo cat /proc/self/stack
[<ffffffff81073
[<ffffffff81074
[<ffffffff81782
[<fffffffffffff
$ ls -l /proc/self/stack
-r--r--r-- 1 ubuntu ubuntu 0 Jan 24 04:06 /proc/self/stack
But on Bionic, the file permission is:
$ ls -l /proc/self/stack
-r-------- 1 ubuntu ubuntu 0 Jan 24 12:07 /proc/self/stack