Sasha Levin <[email protected]> writes: What is the justification for backporting this and the other similar Documentation commits?
These commits just introduce a define _FIXME with value of 0, to document that the userspace ABI was handled incorrectly long ago. These commits do not fix anything. Thes commits do not change anything except a little how they are handled in siginfo_layout. And I don't see the changes that introduce siginfo_layout in kernel/signal.c being backported. Further these commits don't even have a fixes tag so I am curious what is triggering them for backport. Eric > From: "Eric W. Biederman" <[email protected]> > > [ Upstream commit b5daf2b9d1c9a2b4f03ca93f75913ba2da3b3eaa ] > > 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 > that 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. > > This bug is 13 years old and parsic machines are no longer being built > so I don't know if it possible or worth fixing it. But it is at least > worth documenting this so other architectures don't make the same > mistake. > > 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 E.J. Bottomley" <[email protected]> > Cc: Helge Deller <[email protected]> > Cc: [email protected] > Ref: 313c01d3e3fd ("[PATCH] PA-RISC update for 2.6.0") > Histroy Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git > Signed-off-by: "Eric W. Biederman" <[email protected]> > Signed-off-by: Sasha Levin <[email protected]> > --- > arch/parisc/include/uapi/asm/siginfo.h | 7 +++++++ > arch/parisc/kernel/traps.c | 2 +- > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/arch/parisc/include/uapi/asm/siginfo.h > b/arch/parisc/include/uapi/asm/siginfo.h > index 4a1062e05aaf..be40331f757d 100644 > --- a/arch/parisc/include/uapi/asm/siginfo.h > +++ b/arch/parisc/include/uapi/asm/siginfo.h > @@ -8,4 +8,11 @@ > > #include <asm-generic/siginfo.h> > > +/* > + * SIGFPE si_codes > + */ > +#ifdef __KERNEL__ > +#define FPE_FIXME 0 /* Broken dup of SI_USER */ > +#endif /* __KERNEL__ */ > + > #endif > diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c > index 8453724b8009..c919e6c0a687 100644 > --- a/arch/parisc/kernel/traps.c > +++ b/arch/parisc/kernel/traps.c > @@ -629,7 +629,7 @@ void notrace handle_interruption(int code, struct pt_regs > *regs) > si.si_signo = SIGFPE; > /* Set to zero, and let the userspace app figure it out > from > the insn pointed to by si_addr */ > - si.si_code = 0; > + si.si_code = FPE_FIXME; > si.si_addr = (void __user *) regs->iaoq[0]; > force_sig_info(SIGFPE, &si, current); > return;
