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THUNK_TARGET defines [thunk_target] as having "rm" input constraints when CONFIG_RETPOLINE is not set, which isn't constrained enough for this specific case. For inline assembly that modifies the stack pointer before using this input, the underspecification of constraints is dangerous, and results in an indirect call to a previously pushed flags register. In this case `entry`'s stack slot is good enough to satisfy the "m" constraint in "rm", but the inline assembly in handle_external_interrupt_irqoff() modifies the stack pointer via push+pushf before using this input, which in this case results in calling what was the previous state of the flags register, rather than `entry`. Be more specific in the constraints by requiring `entry` be in a register, and not a memory operand. Reported-by: Dmitry Vyukov <dvyukov@google.com> Reported-by: syzbot+3f29ca2efb056a761e38@syzkaller.appspotmail.com Debugged-by: Alexander Potapenko <glider@google.com> Debugged-by: Paolo Bonzini <pbonzini@redhat.com> Debugged-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Message-Id: <20200323191243.30002-1-ndesaulniers@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.