Re: [PATCH stable-4.9] perf callchain: Reference count maps

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Mar 09, 2017 at 09:57:20AM -0800, Krister Johansen wrote:
> commit aa33b9b9a2ebb00d33c83a5312d4fbf2d5aeba36 upstream.
> 
> If dso__load_kcore frees all of the existing maps, but one has already
> been attached to a callchain cursor node, then we can get a SIGSEGV in
> any function that happens to try to use this invalid cursor.  Use the
> existing map refcount mechanism to forestall cleanup of a map until the
> cursor iterates past the node.
> 
> Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: stable@kernel.org
> Fixes: 84c2cafa2889 ("perf tools: Reference count struct map")
> Link: http://lkml.kernel.org/r/20170106062331.GB2707@templeofstupid.com
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  tools/perf/util/callchain.c | 11 +++++++++--
>  tools/perf/util/callchain.h |  6 ++++++
>  tools/perf/util/hist.c      |  7 +++++++
>  3 files changed, 22 insertions(+), 2 deletions(-)
> 
> Apologies for the long lead time on this.  This is the backport that
> I've been using to debug issues on 4.9 kernels in my production
> environment.

Not a problem, thanks for this, now applied.

greg k-h