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  1. 24 4月, 2009 2 次提交
    • O
      check_unsafe_exec: s/lock_task_sighand/rcu_read_lock/ · 437f7fdb
      由 Oleg Nesterov 提交于 
      write_lock(&current->fs->lock) guarantees we can't wrongly miss
LSM_UNSAFE_SHARE, this is what we care about. Use rcu_read_lock()
instead of ->siglock to iterate over the sub-threads. We must see
all CLONE_THREAD|CLONE_FS threads which didn't pass exit_fs(), it
takes fs->lock too.

With or without this patch we can miss the freshly cloned thread
and set LSM_UNSAFE_SHARE, we don't care.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NRoland McGrath <roland@redhat.com>
[ Fixed lock/unlock typo  - Hugh ]
Acked-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      437f7fdb
    • O
      do_execve() must not clear fs->in_exec if it was set by another thread · 8c652f96
      由 Oleg Nesterov 提交于 
      If do_execve() fails after check_unsafe_exec(), it clears fs->in_exec
unconditionally. This is wrong if we race with our sub-thread which
also does do_execve:

	Two threads T1 and T2 and another process P, all share the same
	->fs.

	T1 starts do_execve(BAD_FILE). It calls check_unsafe_exec(), since
	->fs is shared, we set LSM_UNSAFE but not ->in_exec.

	P exits and decrements fs->users.

	T2 starts do_execve(), calls check_unsafe_exec(), now ->fs is not
	shared, we set fs->in_exec.

	T1 continues, open_exec(BAD_FILE) fails, we clear ->in_exec and
	return to the user-space.

	T1 does clone(CLONE_FS /* without CLONE_THREAD */).

	T2 continues without LSM_UNSAFE_SHARE while ->fs is shared with
	another process.

Change check_unsafe_exec() to return res = 1 if we set ->in_exec, and change
do_execve() to clear ->in_exec depending on res.

When do_execve() suceeds, it is safe to clear ->in_exec unconditionally.
It can be set only if we don't share ->fs with another process, and since
we already killed all sub-threads either ->in_exec == 0 or we are the
only user of this ->fs.

Also, we do not need fs->lock to clear fs->in_exec.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Acked-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      8c652f96
  3. 22 4月, 2009 35 次提交
  5. 21 4月, 2009 3 次提交