Messages in this thread | | | Date | Mon, 8 May 2017 21:48:58 +0100 | From | Al Viro <> | Subject | Re: [PATCH v9 1/4] syscalls: Verify address limit before returning to user-mode |
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On Mon, May 08, 2017 at 04:06:35PM +0200, Jann Horn wrote:
> I think Kees might be talking about > https://bugs.chromium.org/p/project-zero/issues/detail?id=822, fixed in > commit e6978e4bf181fb3b5f8cb6f71b4fe30fbf1b655c. The issue was that > perf code that can run in pretty much any context called access_ok().
And that commit has *NOT* solved the problem. perf_callchain_user() can be called synchronously, without passing through that code. Tracepoint shite...
That set_fs() should be done in get_perf_callchain(), just around the call of perf_callchain_user(). Along with pagefault_disable(), actually.
BTW, that's a nice example demonstrating why doing that on the kernel boundary is wrong. Wider (in theory) area being "protected" => easier to miss the ways not crossing its border.
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