On Mon, Feb 20, 2012 at 11:51:41AM -0500, Steven Rostedt wrote: > On Mon, 2012-02-20 at 03:47 -0800, tip-bot for Steven Rostedt wrote: > > Commit-ID: 45d5a1683c04be28abdf5c04c27b1417e0374486 > > Gitweb: http://git.kernel.org/tip/45d5a1683c04be28abdf5c04c27b1417e0374486 > > Author: Steven Rostedt <rostedt@xxxxxxxxxxx> > > AuthorDate: Sun, 19 Feb 2012 16:43:37 -0500 > > Committer: Ingo Molnar <mingo@xxxxxxx> > > CommitDate: Mon, 20 Feb 2012 09:09:57 +0100 > > > > x86/nmi: Test saved %cs in NMI to determine nested NMI case > > > > Currently, the NMI handler tests if it is nested by checking the > > special variable saved on the stack (set during NMI handling) > > and whether the saved stack is the NMI stack as well (to prevent > > the race when the variable is set to zero). > > > > But userspace may set their %rsp to any value as long as they do > > not derefence it, and it may make it point to the NMI stack, > > which will prevent NMIs from triggering while the userspace app > > is running. (I tested this, and it is indeed the case) > > > > Add another check to determine nested NMIs by looking at the > > saved %cs (code segment register) and making sure that it is the > > kernel code segment. > > > > Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > > Cc: H. Peter Anvin <hpa@xxxxxxxxx> > > Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > > Cc: <stable@xxxxxxxxxx> > > Just so that we do not confuse Greg, the bug was introduced in the 3.3 > merge window. It does not exist in 3.2 or earlier. Thanks for letting me know, I would have been confused :) greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html