It turns out that the BUG_ON() in fs/exec.c: de_thread() is unreliable
and can trigger due to the test itself being racy.
de_thread() does
while (atomic_read(&sig->count) > count) {
}
.....
.....
BUG_ON(!thread_group_empty(current));
but release_task does
write_lock_irq(&tasklist_lock)
__exit_signal
(this is where atomic_dec(&sig->count) is run)
__exit_sighand
__unhash_process
takes write lock on tasklist_lock
remove itself out of PIDTYPE_TGID list
write_unlock_irq(&tasklist_lock)
so there's a clear (although small) window between the
atomic_dec(&sig->count) and the actual PIDTYPE_TGID unhashing of the
thread.
And actually there is no need for all threads to have exited at this
point, so we simply kill the BUG_ON.
Big thanks to Marc Lehmann who provided the test-case.
Fixes Bug 5170 (http://bugme.osdl.org/show_bug.cgi?id=5170)
Signed-off-by: Alexander Nyberg <alexn@telia.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In order for the RCU to work, the file table array, sets and their sizes must
be updated atomically. Instead of ensuring this through too many memory
barriers, we put the arrays and their sizes in a separate structure. This
patch takes the first step of putting the file table elements in a separate
structure fdtable that is embedded withing files_struct. It also changes all
the users to refer to the file table using files_fdtable() macro. Subsequent
applciation of RCU becomes easier after this.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When a noninitial thread does exec, it becomes the new group leader. If
there is a ITIMER_REAL timer running, it points at the old group leader and
when it fires it can follow a stale pointer. The timer data needs to be
reset to point at the exec'ing thread that is becoming the group leader.
This has to synchronize with any concurrent firing of the timer to make
sure that it_real_fn can never run when the data points to a thread that
might have been reaped already.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add a new `suid_dumpable' sysctl:
This value can be used to query and set the core dump mode for setuid
or otherwise protected/tainted binaries. The modes are
0 - (default) - traditional behaviour. Any process which has changed
privilege levels or is execute only will not be dumped
1 - (debug) - all processes dump core when possible. The core dump is
owned by the current user and no security is applied. This is intended
for system debugging situations only. Ptrace is unchecked.
2 - (suidsafe) - any binary which normally would not be dumped is dumped
readable by root only. This allows the end user to remove such a dump but
not access it directly. For security reasons core dumps in this mode will
not overwrite one another or other files. This mode is appropriate when
adminstrators are attempting to debug problems in a normal environment.
(akpm:
> > +EXPORT_SYMBOL(suid_dumpable);
>
> EXPORT_SYMBOL_GPL?
No problem to me.
> > if (current->euid == current->uid && current->egid == current->gid)
> > current->mm->dumpable = 1;
>
> Should this be SUID_DUMP_USER?
Actually the feedback I had from last time was that the SUID_ defines
should go because its clearer to follow the numbers. They can go
everywhere (and there are lots of places where dumpable is tested/used
as a bool in untouched code)
> Maybe this should be renamed to `dump_policy' or something. Doing that
> would help us catch any code which isn't using the #defines, too.
Fair comment. The patch was designed to be easy to maintain for Red Hat
rather than for merging. Changing that field would create a gigantic
diff because it is used all over the place.
)
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add some comments about task->comm, to explain what it is near its definition
and provide some important pointers to its uses.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch makes some needlessly global identifiers static.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Arjan van de Ven <arjanv@infradead.org>
Acked-by: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Alexander Nyberg