Messages in this thread | | | Date | Thu, 23 Sep 2021 18:01:51 -0700 | From | Kees Cook <> | Subject | /proc/$pid/chan kernel address exposures (was Re: [proc/wchan] 30a3a19273: leaking-addresses.proc.wchan./proc/bus/input/devices:B:KEY=1000000000007ff980000000007fffebeffdfffeffffffffffffffffffffe) |
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On Sun, Jan 03, 2021 at 07:25:36PM +0100, Helge Deller wrote: > On 1/3/21 3:27 PM, kernel test robot wrote: > > FYI, we noticed the following commit (built with gcc-9): > > > > commit: 30a3a192730a997bc4afff5765254175b6fb64f3 ("[PATCH] proc/wchan: Use printk format instead of lookup_symbol_name()") > > url: https://github.com/0day-ci/linux/commits/Helge-Deller/proc-wchan-Use-printk-format-instead-of-lookup_symbol_name/20201218-010048 > > base: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git 09162bc32c880a791c6c0668ce0745cf7958f576 > > > > in testcase: leaking-addresses > > version: leaking-addresses-x86_64-4f19048-1_20201111 > > [...] > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): > > I don't see anything wrong with the wchan patch (30a3a192730a997bc4afff5765254175b6fb64f3), > or that it could have leaked anything. > > Maybe the kernel test robot picked up the wchan patch by mistake ? > > > [...] > > [2 wchan] 0xffffc9000000003c ^^^^^
As the root cause of a kernel address exposure, Jann pointed out[2] commit 152c432b128c, which I've tracked to here, only to discover this regression was, indeed, reported. :(
So, we have a few things:
1) wchan has been reporting "0" in the default x86 config (ORC unwinder) for 4 years now.
2) non-x86 or non-ORC, wchan has been leaking raw kernel addresses since commit 152c432b128c (v5.12).
3) the output of scripts/leaking_addresses.pl is hard to read. :)
We can fix 1 and 2 with: https://lore.kernel.org/lkml/20210923233105.4045080-1-keescook@chromium.org/ (though that will need a Cc: stable now...)
If we don't do that, we still need to revert 152c432b128c in v5.12 and later.
We should likely make leaking_addresses.pl a little more readable while we're at it.
-Kees
[1] https://lore.kernel.org/lkml/20210921193249.el476vlhg5k6lfcq@shells.gnugeneration.com/ [2] https://lore.kernel.org/lkml/CAG48ez2zC=+PuNgezH53HBPZ8CXU5H=vkWx7nJs60G8RXt3w0Q@mail.gmail.com/
-- Kees Cook
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