Messages in this thread | | | Date | Wed, 13 Oct 2021 18:41:01 -0700 | From | Josh Poimboeuf <> | Subject | Re: [PATCH] x86/unwind/orc: Handle kretprobes_trampoline |
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On Mon, Oct 11, 2021 at 02:03:26PM -0700, Kees Cook wrote: > On Thu, Sep 02, 2021 at 07:13:26PM -0700, Kees Cook wrote: > > From: Marios Pomonis <pomonis@google.com> > > > > Fix a bug in the ORC unwinder when kretprobes has replaced a return > > address with the address of `kretprobes_trampoline'. ORC mistakenly > > assumes that the address in the stack is a return address and decrements > > it by 1 in order to find the proper depth of the next frame. > > > > This issue was discovered while testing the FG-KASLR series[0][1] and > > running the live patching test[2] that was originally failing[3]. > > > > [0] https://lore.kernel.org/kernel-hardening/20200923173905.11219-1-kristen@linux.intel.com/ > > [1] https://github.com/KSPP/linux/issues/132 > > [2] https://github.com/lpechacek/qa_test_klp > > [3] https://lore.kernel.org/lkml/alpine.LSU.2.21.2009251450260.13615@pobox.suse.cz/ > > > > Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder") > > Signed-off-by: Marios Pomonis <pomonis@google.com> > > Cc: Josh Poimboeuf <jpoimboe@redhat.com> > > Cc: Alexander Lobakin <alexandr.lobakin@intel.com> > > Cc: Kristen C Accardi <kristen.c.accardi@intel.com> > > Cc: Sami Tolvanen <samitolvanen@google.com> > > Signed-off-by: Kees Cook <keescook@chromium.org> > > Ping again; Josh can you take this please?
I'm confused how this still fixes anything after Masami's patch set, which is now in linux-next.
After those patches, for a CALL-type ORC entry, the unwinder sets state->ip to the address returned by unwind_recover_ret_addr(). In the case of a kretprobe, that means that state->ip will no longer point to kretprobes_trampoline() -- making the above patch description incorrect.
Instead, state->ip will then contain the original call return address which was replaced by kretpobes. So it looks to the unwinder like a normal call return address, and 'state->signal' should remain false.
Am I missing something?
-- Josh
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