Messages in this thread | | | Date | Mon, 30 Mar 2009 03:40:40 +0200 | From | Oleg Nesterov <> | Subject | Re: Q: check_unsafe_exec() races (Was: [PATCH 2/4] fix setuid sometimes doesn't) |
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On 03/30, Oleg Nesterov wrote: > > On 03/30, Al Viro wrote: > > > > On Mon, Mar 30, 2009 at 02:08:43AM +0100, Al Viro wrote: > > > > > So... > > > * check_unsafe_exec() locks current->fs shared, goes through all > > > threads comparing their ->fs with our, if the number doesn't match - bail > > > out. Otherwise we mark it "under exec". > > Unless I missed something again, check_unsafe_exec() should check "under exec" > after it takes fs->lock. If set - we are racing with sub-thread, return -EAGAIN. > > We can't proceed. If that another exec() fails, it will clear "under exec" at > the end of do_execve(), before we kill other threads.
Or we need a counter to mark/unmark.
Oleg.
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