signal/metag: Document a conflict with SI_USER with SIGFPE

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Setting si_code to 0 results in a userspace seeing an si_code of 0.
This is the same si_code as SI_USER.  Posix and common sense requires
that SI_USER not be a signal specific si_code.  As such this use of 0
for the si_code is a pretty horribly broken ABI.

Further use of si_code == 0 guaranteed that copy_siginfo_to_user saw a
value of __SI_KILL and now sees a value of SIL_KILL with the result
hat uid and pid fields are copied and which might copying the si_addr
field by accident but certainly not by design.  Making this a very
flakey implementation.

Utilizing FPE_FIXME siginfo_layout will now return SIL_FAULT and the
appropriate fields will reliably be copied.

Possible ABI fixes includee:
  - Send the signal without siginfo
  - Don't generate a signal
  - Possibly assign and use an appropriate si_code
  - Don't handle cases which can't happen

Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-metag@vger.kernel.org
Ref: ac919f0883 ("metag: Traps")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

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This commit is contained in:

Eric W. Biederman 2017-08-01 10:37:40 -05:00

parent b5daf2b9d1

commit b80328be53

2 changed files with 8 additions and 1 deletions

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7

arch/metag/include/uapi/asm/siginfo.h

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2

arch/metag/kernel/traps.c

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