7055197705709c59b8ab77e6a5c7d46d61edd96e
Author: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
c6c75deda813
1fde6f21d90f
> -----Original Message-----
> From: David Laight <David.Laight@xxxxxxxxxx>
> Sent: 04 September 2022 15:05
>
> Sometime after 5.10.105 (5.10.132 and 6.0) there is a change that
> makes setns(open("/proc/1/ns/net")) in the main process change
> the behaviour of other process threads.
>
> I don't know how much is broken, but the following fails.
>
> Create a network namespace (eg "test").
> Create a 'bond' interface (eg "test0") in the namespace.
>
> Then /proc/net/bonding/test0 only exists inside the namespace.
>
> However if you run a program in the "test" namespace that does:
> - create a thread.
> - change the main thread to in "init" namespace.
> - try to open /proc/net/bonding/test0 in the thread.
> then the open fails.
>
> I don't know how much else is affected and haven't tried
> to bisect (I can't create bonds on my normal test kernel).
I've now bisected it.
Prior to change 7055197705709c59b8ab77e6a5c7d46d61edd96e
proc: fix dentry/inode overinstantiating under /proc/${pid}/net
the setns() had no effect of either thread.
Afterwards both threads see the entries in the init namespace.
However I think that in 5.10.105 the setns() did affect
the thread it was run in.
That might be the behaviour before c6c75deda813.
proc: fix lookup in /proc/net subdirectories after setns(2)
There is also the earlier 1fde6f21d90f
proc: fix /proc/net/* after setns(2)
>From the commit messages it does look as though setns() should
change what is seen, but just for the current thread.
So it is currently broken - and has been since 5.18.0-rc4
and whichever stable branches the change was backported to.
David
>
> The test program below shows the problem.
> Compile and run as:
> # ip netns exec test strace -f test_prog /proc/net/bonding/test0
>
> The second open by the child should succeed, but fails.
>
> I can't see any changes to the bonding code, so I suspect
> it is something much more fundamental.
> It might only affect /proc/net, but it might also affect
> which namespace sockets get created in.
> IIRC ls -l /proc/n/task/*/ns gives the correct namespaces.
>
> David
>
>
> #define _GNU_SOURCE
>
> #include <fcntl.h>
> #include <unistd.h>
> #include <poll.h>
> #include <pthread.h>
> #include <sched.h>
>
> #define delay(secs) poll(0,0, (secs) * 1000)
>
> static void *thread_fn(void *file)
> {
> delay(2);
> open(file, O_RDONLY);
>
> delay(5);
> open(file, O_RDONLY);
>
> return NULL;
> }
>
> int main(int argc, char **argv)
> {
> pthread_t id;
>
> pthread_create(&id, NULL, thread_fn, argv[1]);
>
> delay(1);
> open(argv[1], O_RDONLY);
>
> delay(2);
> setns(open("/proc/1/ns/net", O_RDONLY), 0);
>
> delay(1);
> open(argv[1], O_RDONLY);
>
> delay(4);
>
> return 0;
> }
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
